Check deprecated_call specific to deprecation

`deprecated_call` used to accept any warning. As of pytest-dev#897, it
is now specific to DeprecationWarnings, and another commit in
this PR extends this to PendingDeprecationWarnings. This commit
makes sure this stays the case.

Author: hunse

CHANGELOG

@@ -1,6 +1,11 @@
 2.8.1.dev
 ---------
 
+- 'deprecated_call' is now only satisfied with a DeprecationWarning or
+  PendingDeprecationWarning. Before 2.8.0, it accepted any warning, and 2.8.0
+  made it accept only DeprecationWarning (but not PendingDeprecationWarning).
+  Thanks Alex Gaynor for the issue and Eric Hunsberger for the PR.
+
 - fix issue #1073: avoid calling __getattr__ on potential plugin objects.
   This fixes an incompatibility with pytest-django.  Thanks Andreas Pelme,
   Bruno Oliveira and Ronny Pfannschmidt for contributing and Holger Krekel

testing/test_recwarn.py

@@ -115,6 +115,14 @@ def test_deprecated_call_pending(self):
         f = lambda: py.std.warnings.warn(PendingDeprecationWarning("hi"))
         pytest.deprecated_call(f)
 
+    def test_deprecated_call_specificity(self):
+        other_warnings = [Warning, UserWarning, SyntaxWarning, RuntimeWarning,
+                          FutureWarning, ImportWarning, UnicodeWarning]
+        for warning in other_warnings:
+            f = lambda: py.std.warnings.warn(warning("hi"))
+            with pytest.raises(AssertionError):
+                pytest.deprecated_call(f)
+
 
 class TestWarns(object):
     def test_strings(self):