Add compatibility with newer versions of pytest.

Taken from upstream:

  https://github.com/dateutil/dateutil/commit/2bdd63158b7f981fc6d70a869680451bdfd8d848

diff --git a/dateutil/test/test_internals.py b/dateutil/test/test_internals.py
index 53081314..b32e6723 100644
--- a/dateutil/test/test_internals.py
+++ b/dateutil/test/test_internals.py
@@ -9,6 +9,7 @@
 
 import sys
 import pytest
+import warnings
 
 from dateutil.parser._parser import _ymd
 from dateutil import tz
@@ -65,18 +66,17 @@ def test_parser_parser_private_not_warns():
     from dateutil.parser._parser import _timelex, _tzparser
     from dateutil.parser._parser import _parsetz
 
-    with pytest.warns(None) as recorder:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
         _tzparser()
-        assert len(recorder) == 0
 
-    with pytest.warns(None) as recorder:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
         _timelex('2014-03-03')
 
-        assert len(recorder) == 0
-
-    with pytest.warns(None) as recorder:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
         _parsetz('+05:00')
-        assert len(recorder) == 0
 
 
 @pytest.mark.tzstr
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<tr><td><span title='2022-01-09 11:35:59 +0100'>2022-01-09</span></td><td><a href='/guix/commit/po/doc/guix-cookbook.fa.po?id=934b0cdfee2078bad42429427e12d6ee2ddb7fec'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.fi.po: New file.
* po/doc/guix-manual.fi.po: New file.
* po/doc/local.mk: Add them.
* doc/local.mk: Add them.
* po/guix/fi.po: New file.
* po/guix/LINGUAS: Add it.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-10-17 22:10:25 +0200'>2021-10-17</span></td><td><a href='/guix/commit/po/doc/guix-cookbook.fa.po?id=15c91189cb61c579f4289047c79530cefe75215f'>nls: Update translations.</a></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-09-02 04:06:52 +0200'>2021-09-02</span></td><td><a href='/guix/commit/po/doc/guix-cookbook.fa.po?id=1ff2092a39dc5c7c7cd9b4a0ba4b59f92e738efc'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/packages/it.po: New file.
* po/packages/LINGUAS: Add `it'.
* po/*/*.po: Update translations.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-08-04 14:49:53 +0200'>2021-08-04</span></td><td><a href='/guix/commit/po/doc/guix-cookbook.fa.po?id=6c10c96fedf707d7be059aeb79bd5c8e2d2fa210'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.ru.po: New file.
* po/doc/guix-cookbook.sk.po: New file.
* po/*/*.po: Update translations.
* doc/local.mk (COOKBOOK_LANGUAGES): Add ru and sk.
(info_TEXINFOS): Add Russian and Slovak cookbooks.
* po/doc/local.mk (DOC_COOKBOOK_PO_FILES): Add Russian and Slovak po
files.
</span></span></td><td>Julien Lepiller</td></tr>