Add dummy canvas to test

Author: m-kuhn

tests/src/python/test_qgsrelationeditwidget.py

@@ -29,7 +29,8 @@
 from qgis.gui import (
     QgsGui,
     QgsRelationWidgetWrapper,
-    QgsAttributeEditorContext
+    QgsAttributeEditorContext,
+    QgsMapCanvas
 )
 
 from qgis.PyQt.QtCore import QTimer
@@ -47,7 +48,8 @@ def setUpClass(cls):
         Setup the involved layers and relations for a n:m relation
         :return:
         """
-        QgsGui.editorWidgetRegistry().initEditors()
+        cls.mapCanvas = QgsMapCanvas()
+        QgsGui.editorWidgetRegistry().initEditors(cls.mapCanvas)
         cls.dbconn = 'service=\'qgis_test\''
         if 'QGIS_PGTEST_DB' in os.environ:
             cls.dbconn = os.environ['QGIS_PGTEST_DB']