Make _strptime.TimeRE().pattern() use ``\s+`` for matching whitespace instead
of ``\s*``.  This prevents patterns from "stealing" bits from other patterns in
order to make a match work.

Closes bug #1730389.  Will be backported.
diff --git a/Lib/_strptime.py b/Lib/_strptime.py
index 9e7823a..166cf82 100644
--- a/Lib/_strptime.py
+++ b/Lib/_strptime.py
@@ -250,7 +250,7 @@
         regex_chars = re_compile(r"([\\.^$*+?\(\){}\[\]|])")
         format = regex_chars.sub(r"\\\1", format)
         whitespace_replacement = re_compile('\s+')
-        format = whitespace_replacement.sub('\s*', format)
+        format = whitespace_replacement.sub('\s+', format)
         while '%' in format:
             directive_index = format.index('%')+1
             processed_format = "%s%s%s" % (processed_format,