Fallback to the original behavior if prefix is not available (#1068)

I needed to restore the original behavior because some external
applications was actually relying on the behavior.

https://github.com/apache/incubator-airflow/blob/1.8.0/airflow/bin/cli.py#L775

gunicorn/app/base.py

@@ -111,12 +111,15 @@ def load_config_from_module_name_or_filename(self, location):
         if location.startswith("python:"):
             module_name = location[len("python:"):]
             cfg = self.get_config_from_module_name(module_name)
-        else:
-            if location.startswith("file:"):
-                filename = location[len("file:"):]
-            else:
-                filename = location
+        elif location.startswith("file:"):
+            filename = location[len("file:"):]
             cfg = self.get_config_from_filename(filename)
+        else:
+            # Fallback to the original behavior if prefix is not available (#1068)
+            try:
+                cfg = self.get_config_from_module_name(module_name=location)
+            except ImportError:
+                cfg = self.get_config_from_filename(filename=location)
 
         for k, v in cfg.items():
             # Ignore unknown names