gnu: python-parse: Fix failing test.

* gnu/packages/python.scm (python-parse)[origin]: Add patch.
* gnu/packages/patches/python-parse-too-many-fields.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/packages/patches/python-parse-too-many-fields.patch

@@ -0,0 +1,52 @@
+From 32f15cfefb7c7b6476360ac65cba807aa3dfccfa Mon Sep 17 00:00:00 2001
+From: David King <dking@redhat.com>
+Date: Mon, 14 Dec 2015 09:58:19 +0000
+Subject: [PATCH] Fix test_too_many_fields with Python 3.5
+
+taken from https://github.com/r1chardj0n3s/parse/pull/34
+
+Python versions before 3.5 had a limit of 100 groups in regular
+expressions. This limit was removed during 3.5 development:
+
+http://bugs.python.org/issue22437
+https://hg.python.org/cpython/rev/0b85ea4bd1af
+
+The test_too_many_fields test asserts that the limit exists by
+attempting to parse a string with 15 fields, which triggers the 100
+named groups limit.
+
+Adjust the test so that if first checks to see whether the limit of 100
+named groups exists, and only assert that parsing 15 fields fails if
+that is the case.
+---
+ test_parse.py | 10 ++++++++--
+ 1 file changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/test_parse.py b/test_parse.py
+index c524349..1d50568 100755
+--- a/test_parse.py
++++ b/test_parse.py
+@@ -6,6 +6,7 @@
+ 
+ import unittest
+ from datetime import datetime, time
++import re
+ 
+ import parse
+ 
+@@ -624,8 +625,13 @@ def test_mixed_type_variant(self):
+         self.assertEqual(r.fixed[21], 'spam')
+ 
+     def test_too_many_fields(self):
+-        p = parse.compile('{:ti}' * 15)
+-        self.assertRaises(parse.TooManyFields, p.parse, '')
++        # Python 3.5 removed the limit of 100 named groups in a regular expression,
++        # so only test for the exception if the limit exists.
++        try:
++            re.compile("".join("(?P<n{n}>{n}-)".format(n=i) for i in range(101)))
++        except AssertionError:
++            p = parse.compile('{:ti}' * 15)
++            self.assertRaises(parse.TooManyFields, p.parse, '')
+ 
+ 
+ class TestSearch(unittest.TestCase):