restore QGIS 3.18 compatibility

[Andreas Janz]

Recent commits intoduced some QGIS 3.20 features not available in 3.18. E.g.

Qgis.VectorExportResult

Qgis.BrowserItemType

Not sure if there is more stuff from 3.20 only is used.

[Andreas Janz]

e.g. “Load Example Data” won’t work anymore:
Traceback (most recent call last):
File "D:\source\QGISPlugIns\enmap-box\enmapbox\gui\enmapboxgui.py", line 1046, in <lambda>
mapWindows=1 if len(self.mDockManager.docks(MapDock)) == 0 else 0))
File "D:\source\QGISPlugIns\enmap-box\enmapbox\gui\enmapboxgui.py", line 1561, in openExampleData
self.addSources(files)
File "D:\source\QGISPlugIns\enmap-box\enmapbox\gui\enmapboxgui.py", line 1779, in addSources
return self.mDataSourceManager.addDataSources(sourceList)
File "D:\source\QGISPlugIns\enmap-box\enmapbox\gui\datasources\manager.py", line 252, in addDataSources
sources = DataSourceFactory.create(sources, provider=provider, name=name)
File "D:\source\QGISPlugIns\enmap-box\enmapbox\gui\datasources\manager.py", line 678, in create
results.extend(DataSourceFactory.create(s, provider=provider, name=name))
File "D:\source\QGISPlugIns\enmap-box\enmapbox\gui\datasources\manager.py", line 725, in create
dataItem = QgsDataItem(Qgis.BrowserItemType.Custom, None, name, source, 'special:file')
AttributeError: type object 'Qgis' has no attribute 'BrowserItemType'

[Benjamin Jakimow]

should be fixed, please re-test

[Andreas Janz]

Looks good