extensions_framework: make util.path_relative_to_export more robust on win32

modules/extensions_framework/util.py

@@ -52,8 +52,15 @@ def path_relative_to_export(p):
 	"""Return a path that is relative to the export path"""
 	global export_path
 	p = filesystem_path(p)
+	ep = os.path.dirname(export_path)
+	
+	if os.sys.platform == 'win32':
+		# Prevent an error whereby python thinks C: and c: are different drives
+		if p[1] == ':': p = p[0].lower() + p[1:]
+		if ep[1] == ':': ep = ep[0].lower() + ep[1:]
+	
 	try:
-		relp = os.path.relpath(p, os.path.dirname(export_path))
+		relp = os.path.relpath(p, ep)
 	except ValueError: # path on different drive on windows
 		relp = p