#27364: fix "incorrect" uses of escape character in the stdlib.

And most of the tools.

Patch by Emanual Barry, reviewed by me, Serhiy Storchaka, and
Martin Panter.
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 86c9373..988c6f7 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -4001,12 +4001,12 @@
                              datetime(xx, xx, xx, xx, xx, xx, xx))
 
         with self.assertRaisesRegex(TypeError, '^an integer is required '
-                                               '\(got type str\)$'):
+                                              r'\(got type str\)$'):
             datetime(10, 10, '10')
 
         f10 = Number(10.9)
         with self.assertRaisesRegex(TypeError, '^__int__ returned non-int '
-                                               '\(type float\)$'):
+                                              r'\(type float\)$'):
             datetime(10, 10, f10)
 
         class Float(float):