Issue #13938: 2to3 converts StringTypes to a tuple. Patch from Mark Hammond.

Lib/lib2to3/fixes/fix_types.py

@@ -42,7 +42,7 @@ _TYPE_MAPPING = {
         'NotImplementedType' : 'type(NotImplemented)',
         'SliceType' : 'slice',
         'StringType': 'bytes', # XXX ?
-        'StringTypes' : 'str', # XXX ?
+        'StringTypes' : '(str,)', # XXX ?
         'TupleType': 'tuple',
         'TypeType' : 'type',
         'UnicodeType': 'str',

Lib/lib2to3/tests/test_fixers.py

@@ -3263,6 +3263,10 @@ class Test_types(FixerTestCase):
         a = """type(None)"""
         self.check(b, a)
 
+        b = "types.StringTypes"
+        a = "(str,)"
+        self.check(b, a)
+
 class Test_idioms(FixerTestCase):
     fixer = "idioms"
 

Misc/NEWS

@@ -34,6 +34,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #13938: 2to3 converts StringTypes to a tuple. Patch from Mark Hammond.
+
 - Issue #24611: Fixed compiling the posix module on non-Windows platforms
   without mknod() or makedev() (e.g. on Unixware).