fix race condition

theano/gof/lazylinker_c.py

@@ -30,6 +30,18 @@ try:
     # compile_str()) but if another lazylinker_ext does exist then it will be
     # imported and compile_str won't get called at all.
     location = os.path.join(config.compiledir, 'lazylinker_ext')
+    try:
+        # Try to make the location
+        os.mkdir(location)
+    except OSError, e:
+        # If we get an error, verify that the error was # 17, the path already exists,
+        # and that it is a directory
+        # Note: we can't check if it exists before making it, because we are not holding
+        # the lock right now, so we could race another process and get error 17 if we lose
+        # the race
+        assert 'Errno 17' in str(e)
+        assert os.path.isdir(location)
+
     if not os.path.exists(location):
         os.mkdir(location)
     if not os.path.exists(os.path.join(location, '__init__.py')):