This extension is corrupted : No module named qgscollapsiblegroupbox

Question

I'm building a QGIS plugin, and I am making the GUI using Qt Designer.

Whenever I am using one of the "QGIS custom widgets" (in the present case, a QgsCollapsibleGroupBox) in my plugin window, it doesn't work anymore. If it's a new plugin and isn't installed yet, it is flagged as corrupted, with the error "No module named qgscollapsiblegroupbox". And if I modify the GUI of an existing plugin, I got the same error but with a bit more details :

Traceback (most recent call last):

File "C:/OSGEO4~1/apps/qgis-ltr/./python\qgis\utils.py", line 219, in startPlugin plugins[packageName] = package.classFactory(iface)

File "C:/Users/eltheo/.qgis2/python/plugins\myplugin__init__.py", line 34, in classFactory from .myplugin import myplugin

File "C:/OSGEO4~1/apps/qgis-ltr/./python\qgis\utils.py", line 478, in _import mod = _builtin_import(name, globals, locals, fromlist, level)

File "C:/Users/eltheo/.qgis2/python/plugins\myplugin\myplugin.py", line 31, in from list_dockwidget import listDockWidget

File "C:/OSGEO4~1/apps/qgis-ltr/./python\qgis\utils.py", line 478, in _import mod = _builtin_import(name, globals, locals, fromlist, level)

File "C:/Users/eltheo/.qgis2/python/plugins\myplugin\myplugin_dockwidget.py", line 30, in os.path.dirname(file), 'myplugin_dockwidget_base.ui'))

File "C:\OSGEO4~1\apps\Python27\lib\site-packages\PyQt4\uic__init__.py", line 213, in loadUiType exec(code_string.getvalue(), ui_globals)

File "", line 205, in

File "C:/OSGEO4~1/apps/qgis-ltr/./python\qgis\utils.py", line 478, in _import mod = _builtin_import(name, globals, locals, fromlist, level)

ImportError: No module named qgscollapsiblegroupbox

I had the same problem a couple weeks ago with a QgsFieldComboBox, so I guess the problem lies with all the QGIS custom widgets.

I've looked in the ui_myplugin.py file that it generated when the plugin is compilated, I've found a line at the very end, that seems to be the problem :

from qgscollapsiblegroupbox import QgsCollapsibleGroupBox

I've try to put that line at the begining of the code with the other import, then to replace it with

from qgis.gui import QgsCollapsibleGroupBox / from qgis.gui import *

But nothing changes, which is odd for the error should at least be different as there is no more mention of "qgscollapsiblegroupbox" in my files.