Also skip librsvg import on AttributeError

In the case python-gobject isn’t installed, but another package (such as
libibus) provides overrides, the gi module will still get imported fine
despite being empty, resulting in a traceback. To prevent this, we also
catch AttributeError so that gi.require_version can fail.

poezio/windows/image.py

@@ -20,7 +20,7 @@ try:
     from gi.repository import Rsvg
     import cairo
     HAS_RSVG = True
-except (ImportError, ValueError):
+except (ImportError, ValueError, AttributeError):
     HAS_RSVG = False
 
 from poezio.windows.base_wins import Win