--- firefox-81.0.1/build/mach_initialize.py.old	2020-10-06 14:16:06.212974910 +0200
+++ firefox-81.0.1/build/mach_initialize.py	2020-10-06 14:19:03.313179557 +0200
@@ -507,7 +507,10 @@ class ImportHook(object):
         # doesn't happen or because it doesn't matter).
         if not os.path.exists(module.__file__[:-1]):
             if os.path.exists(module.__file__):
-                os.remove(module.__file__)
+                try:
+                    os.remove(module.__file__)
+                except:
+                    pass
             del sys.modules[module.__name__]
             module = self(name, globals, locals, fromlist, level)
 
