Fix test for py37

In previous Python versions, the list of warnigns appears like:

	... list of emitted warnings is: [UserWarning('user',)].

In Python 3.7 apparently the string representation has been improved to:

	... list of emitted warnings is: [UserWarning('user')].

Fix pytest-dev#3011

Author: nicoddemus

testing/test_recwarn.py

@@ -205,14 +205,14 @@ def test_as_contextmanager(self):
         with pytest.raises(pytest.fail.Exception) as excinfo:
             with pytest.warns(RuntimeWarning):
                 warnings.warn("user", UserWarning)
-        excinfo.match(r"DID NOT WARN. No warnings of type \(.+RuntimeWarning.+,\) was emitted. "
-                      r"The list of emitted warnings is: \[UserWarning\('user',\)\].")
+        excinfo.match(r"DID NOT WARN. No warningas of type \(.+RuntimeWarning.+,\) was emitted. "
+                      r"The list of emitted warnings is: \[UserWarning\('user',?\)\].")
 
         with pytest.raises(pytest.fail.Exception) as excinfo:
             with pytest.warns(UserWarning):
                 warnings.warn("runtime", RuntimeWarning)
         excinfo.match(r"DID NOT WARN. No warnings of type \(.+UserWarning.+,\) was emitted. "
-                      r"The list of emitted warnings is: \[RuntimeWarning\('runtime',\)\].")
+                      r"The list of emitted warnings is: \[RuntimeWarning\('runtime',?\)\].")
 
         with pytest.raises(pytest.fail.Exception) as excinfo:
             with pytest.warns(UserWarning):