diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
new file mode 100644
index 0000000000..f4a4d0771a
--- /dev/null
+++ b/.gitlab-ci.yml
@@ -0,0 +1,12 @@
+image: registry.gitlab.com/ultimaker/cura/cura-build-environment:centos7
+
+stages:
+  - build
+
+build-and-test:
+  stage: build
+  script:
+    - docker/build.sh
+  artifacts:
+    paths:
+      - build
diff --git a/CMakeLists.txt b/CMakeLists.txt
index be6c9d938e..ba427a745d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,11 +1,10 @@
-project(cura NONE)
-cmake_minimum_required(VERSION 2.8.12)
-
-set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/
-                      ${CMAKE_MODULE_PATH})
+project(cura)
+cmake_minimum_required(VERSION 3.6)
 
 include(GNUInstallDirs)
 
+list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)
+
 set(URANIUM_DIR "${CMAKE_SOURCE_DIR}/../Uranium" CACHE DIRECTORY "The location of the Uranium repository")
 set(URANIUM_SCRIPTS_DIR "${URANIUM_DIR}/scripts" CACHE DIRECTORY "The location of the scripts directory of the Uranium repository")
 
@@ -28,6 +27,26 @@ set(CURA_CLOUD_API_VERSION "" CACHE STRING "Alternative Cura cloud API version")
 configure_file(${CMAKE_SOURCE_DIR}/cura.desktop.in ${CMAKE_BINARY_DIR}/cura.desktop @ONLY)
 configure_file(cura/CuraVersion.py.in CuraVersion.py @ONLY)
 
+
+# FIXME: Remove the code for CMake <3.12 once we have switched over completely.
+# FindPython3 is a new module since CMake 3.12. It deprecates FindPythonInterp and FindPythonLibs. The FindPython3
+# module is copied from the CMake repository here so in CMake <3.12 we can still use it.
+if(${CMAKE_VERSION} VERSION_LESS 3.12)
+    # Use FindPythonInterp and FindPythonLibs for CMake <3.12
+    find_package(PythonInterp 3 REQUIRED)
+
+    set(Python3_EXECUTABLE ${PYTHON_EXECUTABLE})
+
+    set(Python3_VERSION ${PYTHON_VERSION_STRING})
+    set(Python3_VERSION_MAJOR ${PYTHON_VERSION_MAJOR})
+    set(Python3_VERSION_MINOR ${PYTHON_VERSION_MINOR})
+    set(Python3_VERSION_PATCH ${PYTHON_VERSION_PATCH})
+else()
+    # Use FindPython3 for CMake >=3.12
+    find_package(Python3 REQUIRED COMPONENTS Interpreter Development)
+endif()
+
+
 if(NOT ${URANIUM_DIR} STREQUAL "")
     set(CMAKE_MODULE_PATH "${URANIUM_DIR}/cmake")
 endif()
@@ -40,12 +59,12 @@ if(NOT ${URANIUM_SCRIPTS_DIR} STREQUAL "")
     CREATE_TRANSLATION_TARGETS()
 endif()
 
-find_package(PythonInterp 3.5.0 REQUIRED)
 
 install(DIRECTORY resources
         DESTINATION ${CMAKE_INSTALL_DATADIR}/cura)
 install(DIRECTORY plugins
         DESTINATION lib${LIB_SUFFIX}/cura)
+
 if(NOT APPLE AND NOT WIN32)
     install(FILES cura_app.py
             DESTINATION ${CMAKE_INSTALL_BINDIR}
@@ -53,16 +72,16 @@ if(NOT APPLE AND NOT WIN32)
             RENAME cura)
     if(EXISTS /etc/debian_version)
         install(DIRECTORY cura
-            DESTINATION lib${LIB_SUFFIX}/python${PYTHON_VERSION_MAJOR}/dist-packages
+            DESTINATION lib${LIB_SUFFIX}/python${Python3_VERSION_MAJOR}/dist-packages
             FILES_MATCHING PATTERN *.py)
         install(FILES ${CMAKE_BINARY_DIR}/CuraVersion.py
-            DESTINATION lib${LIB_SUFFIX}/python${PYTHON_VERSION_MAJOR}/dist-packages/cura)
+            DESTINATION lib${LIB_SUFFIX}/python${Python3_VERSION_MAJOR}/dist-packages/cura)
     else()
         install(DIRECTORY cura
-            DESTINATION lib${LIB_SUFFIX}/python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}/site-packages
+            DESTINATION lib${LIB_SUFFIX}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages
             FILES_MATCHING PATTERN *.py)
         install(FILES ${CMAKE_BINARY_DIR}/CuraVersion.py
-            DESTINATION lib${LIB_SUFFIX}/python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}/site-packages/cura)
+            DESTINATION lib${LIB_SUFFIX}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages/cura)
     endif()
     install(FILES ${CMAKE_BINARY_DIR}/cura.desktop
             DESTINATION ${CMAKE_INSTALL_DATADIR}/applications)
@@ -78,8 +97,8 @@ else()
             DESTINATION ${CMAKE_INSTALL_BINDIR}
             PERMISSIONS OWNER_READ OWNER_WRITE OWNER_EXECUTE GROUP_READ GROUP_EXECUTE WORLD_READ WORLD_EXECUTE)
     install(DIRECTORY cura
-            DESTINATION lib${LIB_SUFFIX}/python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}/site-packages
+            DESTINATION lib${LIB_SUFFIX}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages
             FILES_MATCHING PATTERN *.py)
     install(FILES ${CMAKE_BINARY_DIR}/CuraVersion.py
-            DESTINATION lib${LIB_SUFFIX}/python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}/site-packages/cura)
+            DESTINATION lib${LIB_SUFFIX}/python${Python3_VERSION_MAJOR}.${Python3_VERSION_MINOR}/site-packages/cura)
 endif()
diff --git a/cmake/CuraTests.cmake b/cmake/CuraTests.cmake
index b6d04de036..c0762e2b91 100644
--- a/cmake/CuraTests.cmake
+++ b/cmake/CuraTests.cmake
@@ -1,10 +1,21 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
-enable_testing()
+include(CTest)
 include(CMakeParseArguments)
 
-find_package(PythonInterp 3.5.0 REQUIRED)
+# FIXME: Remove the code for CMake <3.12 once we have switched over completely.
+# FindPython3 is a new module since CMake 3.12. It deprecates FindPythonInterp and FindPythonLibs. The FindPython3
+# module is copied from the CMake repository here so in CMake <3.12 we can still use it.
+if(${CMAKE_VERSION} VERSION_LESS 3.12)
+    # Use FindPythonInterp and FindPythonLibs for CMake <3.12
+    find_package(PythonInterp 3 REQUIRED)
+
+    set(Python3_EXECUTABLE ${PYTHON_EXECUTABLE})
+else()
+    # Use FindPython3 for CMake >=3.12
+    find_package(Python3 REQUIRED COMPONENTS Interpreter Development)
+endif()
 
 add_custom_target(test-verbose COMMAND ${CMAKE_CTEST_COMMAND} --verbose)
 
@@ -36,7 +47,7 @@ function(cura_add_test)
     if (NOT ${test_exists})
         add_test(
             NAME ${_NAME}
-            COMMAND ${PYTHON_EXECUTABLE} -m pytest --verbose --full-trace --capture=no --no-print-log --junitxml=${CMAKE_BINARY_DIR}/junit-${_NAME}.xml ${_DIRECTORY}
+            COMMAND ${Python3_EXECUTABLE} -m pytest --verbose --full-trace --capture=no --no-print-log --junitxml=${CMAKE_BINARY_DIR}/junit-${_NAME}.xml ${_DIRECTORY}
         )
         set_tests_properties(${_NAME} PROPERTIES ENVIRONMENT LANG=C)
         set_tests_properties(${_NAME} PROPERTIES ENVIRONMENT "PYTHONPATH=${_PYTHONPATH}")
@@ -59,13 +70,13 @@ endforeach()
 #Add code style test.
 add_test(
     NAME "code-style"
-    COMMAND ${PYTHON_EXECUTABLE} run_mypy.py
+    COMMAND ${Python3_EXECUTABLE} run_mypy.py
     WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
 )
 
 #Add test for whether the shortcut alt-keys are unique in every translation.
 add_test(
     NAME "shortcut-keys"
-    COMMAND ${PYTHON_EXECUTABLE} scripts/check_shortcut_keys.py
+    COMMAND ${Python3_EXECUTABLE} scripts/check_shortcut_keys.py
     WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
-)
\ No newline at end of file
+)
diff --git a/cura/OAuth2/AuthorizationHelpers.py b/cura/OAuth2/AuthorizationHelpers.py
index f4a29962a4..08309fa30e 100644
--- a/cura/OAuth2/AuthorizationHelpers.py
+++ b/cura/OAuth2/AuthorizationHelpers.py
@@ -50,6 +50,7 @@ class AuthorizationHelpers:
     #   \param refresh_token:
     #   \return An AuthenticationResponse object.
     def getAccessTokenUsingRefreshToken(self, refresh_token: str) -> "AuthenticationResponse":
+        Logger.log("d", "Refreshing the access token.")
         data = {
             "client_id": self._settings.CLIENT_ID if self._settings.CLIENT_ID is not None else "",
             "redirect_uri": self._settings.CALLBACK_URL if self._settings.CALLBACK_URL is not None else "",
diff --git a/cura/OAuth2/AuthorizationService.py b/cura/OAuth2/AuthorizationService.py
index 1f20f2d87f..d721945b79 100644
--- a/cura/OAuth2/AuthorizationService.py
+++ b/cura/OAuth2/AuthorizationService.py
@@ -68,6 +68,7 @@ class AuthorizationService:
                 self._user_profile = self._parseJWT()
             except requests.exceptions.ConnectionError:
                 # Unable to get connection, can't login.
+                Logger.logException("w", "Unable to validate user data with the remote server.")
                 return None
 
         if not self._user_profile and self._auth_data:
@@ -83,6 +84,7 @@ class AuthorizationService:
     def _parseJWT(self) -> Optional["UserProfile"]:
         if not self._auth_data or self._auth_data.access_token is None:
             # If no auth data exists, we should always log in again.
+            Logger.log("d", "There was no auth data or access token")
             return None
         user_data = self._auth_helpers.parseJWT(self._auth_data.access_token)
         if user_data:
@@ -90,9 +92,11 @@ class AuthorizationService:
             return user_data
         # The JWT was expired or invalid and we should request a new one.
         if self._auth_data.refresh_token is None:
+            Logger.log("w", "There was no refresh token in the auth data.")
             return None
         self._auth_data = self._auth_helpers.getAccessTokenUsingRefreshToken(self._auth_data.refresh_token)
         if not self._auth_data or self._auth_data.access_token is None:
+            Logger.log("w", "Unable to use the refresh token to get a new access token.")
             # The token could not be refreshed using the refresh token. We should login again.
             return None
 
diff --git a/docker/build.sh b/docker/build.sh
new file mode 100755
index 0000000000..88fec8b869
--- /dev/null
+++ b/docker/build.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+
+# Abort at the first error.
+set -e
+
+SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+PROJECT_DIR="$( cd "${SCRIPT_DIR}/.." && pwd )"
+
+# Make sure that environment variables are set properly
+source /opt/rh/devtoolset-7/enable
+export PATH="${CURA_BUILD_ENV_PATH}/bin:${PATH}"
+export PKG_CONFIG_PATH="${CURA_BUILD_ENV_PATH}/lib/pkgconfig:${PKG_CONFIG_PATH}"
+
+cd "${PROJECT_DIR}"
+
+#
+# Clone Uranium and set PYTHONPATH first
+#
+
+# Check the branch to use:
+#  1. Use the Uranium branch with the branch same if it exists.
+#  2. Otherwise, use the default branch name "master"
+URANIUM_BRANCH="${CI_COMMIT_REF_NAME:-master}"
+output="$(git ls-remote --heads https://github.com/Ultimaker/Uranium.git "${URANIUM_BRANCH}")"
+if [ -z "${output}" ]; then
+    echo "Could not find Uranium banch ${URANIUM_BRANCH}, fallback to use master."
+    URANIUM_BRANCH="master"
+fi
+
+echo "Using Uranium branch ${URANIUM_BRANCH} ..."
+git clone --depth=1 -b "${URANIUM_BRANCH}" https://github.com/Ultimaker/Uranium.git "${PROJECT_DIR}"/Uranium
+export PYTHONPATH="${PROJECT_DIR}/Uranium:.:${PYTHONPATH}"
+
+mkdir build
+cd build
+cmake3 \
+    -DCMAKE_BUILD_TYPE=Debug \
+    -DCMAKE_PREFIX_PATH="${CURA_BUILD_ENV_PATH}" \
+    -DURANIUM_DIR="${PROJECT_DIR}/Uranium" \
+    -DBUILD_TESTS=ON \
+    ..
+make
+ctest3 --verbose --output-on-failure -T Test
diff --git a/plugins/GCodeReader/FlavorParser.py b/plugins/GCodeReader/FlavorParser.py
index f8618712a1..4c88e5c953 100644
--- a/plugins/GCodeReader/FlavorParser.py
+++ b/plugins/GCodeReader/FlavorParser.py
@@ -1,31 +1,33 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+import math
+import re
+from typing import Dict, List, NamedTuple, Optional, Union
+
+import numpy
+
 from UM.Backend import Backend
 from UM.Job import Job
 from UM.Logger import Logger
 from UM.Math.Vector import Vector
 from UM.Message import Message
-from cura.Scene.CuraSceneNode import CuraSceneNode
 from UM.i18n import i18nCatalog
 
-catalog = i18nCatalog("cura")
-
 from cura.CuraApplication import CuraApplication
 from cura.LayerDataBuilder import LayerDataBuilder
 from cura.LayerDataDecorator import LayerDataDecorator
 from cura.LayerPolygon import LayerPolygon
+from cura.Scene.CuraSceneNode import CuraSceneNode
 from cura.Scene.GCodeListDecorator import GCodeListDecorator
 from cura.Settings.ExtruderManager import ExtruderManager
 
-import numpy
-import math
-import re
-from typing import Dict, List, NamedTuple, Optional, Union
+catalog = i18nCatalog("cura")
 
 PositionOptional = NamedTuple("Position", [("x", Optional[float]), ("y", Optional[float]), ("z", Optional[float]), ("f", Optional[float]), ("e", Optional[float])])
 Position = NamedTuple("Position", [("x", float), ("y", float), ("z", float), ("f", float), ("e", List[float])])
 
+
 ##  This parser is intended to interpret the common firmware codes among all the
 #   different flavors
 class FlavorParser:
@@ -33,7 +35,7 @@ class FlavorParser:
     def __init__(self) -> None:
         CuraApplication.getInstance().hideMessageSignal.connect(self._onHideMessage)
         self._cancelled = False
-        self._message = None
+        self._message = None  # type: Optional[Message]
         self._layer_number = 0
         self._extruder_number = 0
         self._clearValues()
@@ -425,7 +427,8 @@ class FlavorParser:
 
             if line.startswith("M"):
                 M = self._getInt(line, "M")
-                self.processMCode(M, line, current_position, current_path)
+                if M is not None:
+                    self.processMCode(M, line, current_position, current_path)
 
         # "Flush" leftovers. Last layer paths are still stored
         if len(current_path) > 1:
@@ -463,7 +466,7 @@ class FlavorParser:
             Logger.log("w", "File doesn't contain any valid layers")
 
         settings = CuraApplication.getInstance().getGlobalContainerStack()
-        if not settings.getProperty("machine_center_is_zero", "value"):
+        if settings is not None and not settings.getProperty("machine_center_is_zero", "value"):
             machine_width = settings.getProperty("machine_width", "value")
             machine_depth = settings.getProperty("machine_depth", "value")
             scene_node.setPosition(Vector(-machine_width / 2, 0, machine_depth / 2))
diff --git a/plugins/PostProcessingPlugin/PostProcessingPlugin.py b/plugins/PostProcessingPlugin/PostProcessingPlugin.py
index 78f9cc0516..123733b863 100644
--- a/plugins/PostProcessingPlugin/PostProcessingPlugin.py
+++ b/plugins/PostProcessingPlugin/PostProcessingPlugin.py
@@ -162,7 +162,7 @@ class PostProcessingPlugin(QObject, Extension):
                     loaded_script = importlib.util.module_from_spec(spec)
                     if spec.loader is None:
                         continue
-                    spec.loader.exec_module(loaded_script)
+                    spec.loader.exec_module(loaded_script)  # type: ignore
                     sys.modules[script_name] = loaded_script #TODO: This could be a security risk. Overwrite any module with a user-provided name?
 
                     loaded_class = getattr(loaded_script, script_name)
diff --git a/plugins/UFPReader/UFPReader.py b/plugins/UFPReader/UFPReader.py
index 275726b25b..18527e6450 100644
--- a/plugins/UFPReader/UFPReader.py
+++ b/plugins/UFPReader/UFPReader.py
@@ -38,5 +38,5 @@ class UFPReader(MeshReader):
 
         # Open the GCodeReader to parse the data
         gcode_reader = PluginRegistry.getInstance().getPluginObject("GCodeReader")  # type: ignore
-        gcode_reader.preReadFromStream(gcode_stream)
-        return gcode_reader.readFromStream(gcode_stream)
+        gcode_reader.preReadFromStream(gcode_stream)  # type: ignore
+        return gcode_reader.readFromStream(gcode_stream)  # type: ignore
diff --git a/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDevice.py b/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDevice.py
index fb8e9d9408..43f0a71f6a 100644
--- a/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDevice.py
+++ b/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDevice.py
@@ -93,10 +93,11 @@ class CloudOutputDevice(NetworkedPrinterOutputDevice):
 
         # We use the Cura Connect monitor tab to get most functionality right away.
         if PluginRegistry.getInstance() is not None:
-            self._monitor_view_qml_path = os.path.join(
-                PluginRegistry.getInstance().getPluginPath("UM3NetworkPrinting"),
-                "resources", "qml", "MonitorStage.qml"
-            )
+            plugin_path = PluginRegistry.getInstance().getPluginPath("UM3NetworkPrinting")
+            if plugin_path is None:
+                Logger.log("e", "Cloud not find plugin path for plugin UM3NetworkPrnting")
+                raise RuntimeError("Cloud not find plugin path for plugin UM3NetworkPrnting")
+            self._monitor_view_qml_path = os.path.join(plugin_path, "resources", "qml", "MonitorStage.qml")
 
         # Trigger the printersChanged signal when the private signal is triggered.
         self.printersChanged.connect(self._clusterPrintersChanged)
@@ -158,7 +159,7 @@ class CloudOutputDevice(NetworkedPrinterOutputDevice):
         # the host name should then be "ultimakersystem-aabbccdd0011"
         if network_key.startswith(self.clusterData.host_name):
             return True
-        
+
         # However, for manually added printers, the local IP address is used in lieu of a proper
         # network key, so check for that as well
         if self.clusterData.host_internal_ip is not None and network_key.find(self.clusterData.host_internal_ip):
diff --git a/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDeviceManager.py b/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDeviceManager.py
index 19ec34a6bb..498e141b73 100644
--- a/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDeviceManager.py
+++ b/plugins/UM3NetworkPrinting/src/Cloud/CloudOutputDeviceManager.py
@@ -32,8 +32,8 @@ class CloudOutputDeviceManager:
     # The translation catalog for this device.
     I18N_CATALOG = i18nCatalog("cura")
 
-    addedCloudCluster = Signal(CloudOutputDevice)
-    removedCloudCluster = Signal(CloudOutputDevice)
+    addedCloudCluster = Signal()
+    removedCloudCluster = Signal()
 
     def __init__(self) -> None:
         # Persistent dict containing the remote clusters for the authenticated user.
diff --git a/plugins/UM3NetworkPrinting/src/ClusterUM3OutputDevice.py b/plugins/UM3NetworkPrinting/src/ClusterUM3OutputDevice.py
index 2e3b51546b..d2e18fcb75 100644
--- a/plugins/UM3NetworkPrinting/src/ClusterUM3OutputDevice.py
+++ b/plugins/UM3NetworkPrinting/src/ClusterUM3OutputDevice.py
@@ -66,10 +66,11 @@ class ClusterUM3OutputDevice(NetworkedPrinterOutputDevice):
         self._received_print_jobs = False # type: bool
 
         if PluginRegistry.getInstance() is not None:
-            self._monitor_view_qml_path = os.path.join(
-                PluginRegistry.getInstance().getPluginPath("UM3NetworkPrinting"),
-                "resources", "qml", "MonitorStage.qml"
-            )
+            plugin_path = PluginRegistry.getInstance().getPluginPath("UM3NetworkPrinting")
+            if plugin_path is None:
+                Logger.log("e", "Cloud not find plugin path for plugin UM3NetworkPrnting")
+                raise RuntimeError("Cloud not find plugin path for plugin UM3NetworkPrnting")
+            self._monitor_view_qml_path = os.path.join(plugin_path, "resources", "qml", "MonitorStage.qml")
 
         # Trigger the printersChanged signal when the private signal is triggered
         self.printersChanged.connect(self._clusterPrintersChanged)
diff --git a/tests/Machines/Models/TestDiscoveredPrintersModel.py b/tests/Machines/Models/TestDiscoveredPrintersModel.py
index 4ccc3ba523..28be2536a0 100644
--- a/tests/Machines/Models/TestDiscoveredPrintersModel.py
+++ b/tests/Machines/Models/TestDiscoveredPrintersModel.py
@@ -1,4 +1,4 @@
-from unittest.mock import MagicMock
+from unittest.mock import MagicMock, PropertyMock
 
 import pytest
 
@@ -12,6 +12,8 @@ def discovered_printer_model(application) -> DiscoveredPrintersModel:
 
 def test_discoveredPrinters(discovered_printer_model):
     mocked_device = MagicMock()
+    cluster_size = PropertyMock(return_value = 1)
+    type(mocked_device).clusterSize = cluster_size
 
     mocked_callback = MagicMock()
     discovered_printer_model.addDiscoveredPrinter("ip", "key", "name", mocked_callback, "machine_type", mocked_device)