bpo-35133: Fix mistakes when concatenate string literals on different lines. (GH-10284)

Two kind of mistakes:

1. Missed space. After concatenating there is no space between words.

2. Missed comma. Causes unintentional concatenating in a list of strings.
diff --git a/Lib/importlib/abc.py b/Lib/importlib/abc.py
index dbdd5bf..4b2d3de 100644
--- a/Lib/importlib/abc.py
+++ b/Lib/importlib/abc.py
@@ -66,7 +66,7 @@
 
         """
         warnings.warn("MetaPathFinder.find_module() is deprecated since Python "
-                      "3.4 in favor of MetaPathFinder.find_spec()"
+                      "3.4 in favor of MetaPathFinder.find_spec() "
                       "(available since 3.4)",
                       DeprecationWarning,
                       stacklevel=2)