Have importlib use the repr of a module name in error messages.

This makes it obvious that an import failed because of some extraneous
whitespace (e.g., a newline).

This is a partial fix for issue #8754.

Lib/importlib/_bootstrap.py

@@ -758,7 +758,7 @@ class _ImportLockContext:
 
 _IMPLICIT_META_PATH = [BuiltinImporter, FrozenImporter, _DefaultPathFinder]
 
-_ERR_MSG = 'No module named {}'
+_ERR_MSG = 'No module named {!r}'
 
 def _gcd_import(name, package=None, level=0):
     """Import and return the module based on its name, the package the call is

Misc/NEWS

@@ -84,6 +84,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #8754: Have importlib use the repr of a module name in error messages.
+
 - Issue #11591: Prevent "import site" from modifying sys.path when python
   was started with -S.