Improve quoting in raises match failure message

changelog/5479.bugfix.rst

@@ -0,0 +1 @@
+Improve quoting in ``raises`` match failure message.

src/_pytest/_code/code.py

@@ -544,7 +544,7 @@ class ExceptionInfo:
         """
         __tracebackhide__ = True
         if not re.search(regexp, str(self.value)):
-            assert 0, "Pattern '{!s}' not found in '{!s}'".format(regexp, self.value)
+            assert 0, "Pattern {!r} not found in {!r}".format(regexp, str(self.value))
         return True
 
 

testing/python/raises.py

@@ -220,13 +220,20 @@ class TestRaises:
             int("asdf")
 
         msg = "with base 16"
-        expr = r"Pattern '{}' not found in 'invalid literal for int\(\) with base 10: 'asdf''".format(
+        expr = r"Pattern '{}' not found in \"invalid literal for int\(\) with base 10: 'asdf'\"".format(
             msg
         )
         with pytest.raises(AssertionError, match=expr):
             with pytest.raises(ValueError, match=msg):
                 int("asdf", base=10)
 
+    def test_match_failure_string_quoting(self):
+        with pytest.raises(AssertionError) as excinfo:
+            with pytest.raises(AssertionError, match="'foo"):
+                raise AssertionError("'bar")
+        msg, = excinfo.value.args
+        assert msg == 'Pattern "\'foo" not found in "\'bar"'
+
     def test_raises_match_wrong_type(self):
         """Raising an exception with the wrong type and match= given.