https://github.com/leohemsted/smartypants.py/issues/14
https://github.com/leohemsted/smartypants.py/pull/13

--- smartypants.py-2.0.1/smartypants.py.orig
+++ smartypants.py-2.0.1/smartypants.py
@@ -268,13 +268,13 @@
                 if do_quotes:
                     if t == "'":
                         # Special case: single-character ' token
-                        if re.match("\S", prev_token_last_char):
+                        if re.match(r"\S", prev_token_last_char):
                             t = "’"
                         else:
                             t = "‘"
                     elif t == '"':
                         # Special case: single-character " token
-                        if re.match("\S", prev_token_last_char):
+                        if re.match(r"\S", prev_token_last_char):
                             t = "”"
                         else:
                             t = "“"