Issue #15256: Re-use the ImportError exception message as defined by
importlib._bootstrap in imp to fix a grammatical mistake.

Thanks to Marc Abramowitz for the patch.
diff --git a/Lib/imp.py b/Lib/imp.py
index fcfd3d3..f947c3d 100644
--- a/Lib/imp.py
+++ b/Lib/imp.py
@@ -230,7 +230,7 @@
                 continue
             break  # Break out of outer loop when breaking out of inner loop.
     else:
-        raise ImportError('No module name {!r}'.format(name), name=name)
+        raise ImportError(_bootstrap._ERR_MSG.format(name), name=name)
 
     encoding = None
     if mode == 'U':