Avoid import failure when version is None.

assertion is just for pyflakes it should never raise any exception.

Author: pavoljuhas

diffpy/pdfgui/__init__.py

@@ -21,6 +21,6 @@
 from diffpy.pdfgui.version import __version__
 
 # silence the pyflakes syntax checker
-assert __version__
+assert __version__ or True
 
 # End of file