Has something changed here? I am getting this error when using GSInstance.generate() now:
File "GlyphsApp/GlyphsApp/__init__.py", line 7063, in __GSInstance_Export__
File "GlyphsApp/GlyphsApp/__init__.py", line 6966, in collectResult_instance_title_
AttributeError: 'str' object has no attribute 'stringByAppendingString_'