Update error message

Author: hugovk

Lib/mimetypes.py

@@ -701,7 +701,7 @@ def _main():
             if guess:
                 print('type:', guess, 'encoding:', encoding)
             else:
-                sys.exit(f"error: unknown extension of {gtype}")
+                sys.exit(f"error: media type unknown for {gtype}")
 
 
 if __name__ == '__main__':

Lib/test/test_mimetypes.py

@@ -438,7 +438,7 @@ def test_guess_type_conflicting_with_mimetypes(self):
         retcode, out, err = self.mimetypes_cmd('foo.pic')
         self.assertEqual(retcode, 1)
         self.assertEqual(out, '')
-        self.assertEqual(err, f'error: unknown extension of foo.pic{linesep}')
+        self.assertEqual(err, f'error: media type unknown for foo.pic{linesep}')
 
 if __name__ == "__main__":
     unittest.main()