Fix pytest.raises handling of unicode exceptions in Python 2

changelog/5478.bugfix.rst

@@ -0,0 +1 @@
+Fix encode error when using unicode strings in exceptions with ``pytest.raises``.

src/_pytest/_code/code.py

@@ -572,8 +572,13 @@ def match(self, regexp):
         raised.
         """
         __tracebackhide__ = True
-        if not re.search(regexp, str(self.value)):
-            assert 0, "Pattern '{!s}' not found in '{!s}'".format(regexp, self.value)
+        value = (
+            text_type(self.value) if isinstance(regexp, text_type) else str(self.value)
+        )
+        if not re.search(regexp, value):
+            raise AssertionError(
+                u"Pattern {!r} not found in {!r}".format(regexp, value)
+            )
         return True
 
 

testing/python/raises.py

@@ -4,6 +4,7 @@
 import six
 
 import pytest
+from _pytest.compat import dummy_context_manager
 from _pytest.outcomes import Failed
 from _pytest.warning_types import PytestDeprecationWarning
 
@@ -220,7 +221,7 @@ def test_raises_match(self):
             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):
@@ -278,3 +279,47 @@ def __class__(self):
                 with pytest.raises(CrappyClass()):
                     pass
             assert "via __class__" in excinfo.value.args[0]
+
+
+class TestUnicodeHandling:
+    """Test various combinations of bytes and unicode with pytest.raises (#5478)
+
+    https://github.com/pytest-dev/pytest/pull/5479#discussion_r298852433
+    """
+
+    success = dummy_context_manager
+    py2_only = pytest.mark.skipif(
+        six.PY3, reason="bytes in raises only supported in Python 2"
+    )
+
+    @pytest.mark.parametrize(
+        "message, match, expectation",
+        [
+            (u"\u2603", u"\u2603", success()),
+            (u"\u2603", u"\u2603foo", pytest.raises(AssertionError)),
+            pytest.param(b"hello", b"hello", success(), marks=py2_only),
+            pytest.param(
+                b"hello", b"world", pytest.raises(AssertionError), marks=py2_only
+            ),
+            pytest.param(u"hello", b"hello", success(), marks=py2_only),
+            pytest.param(
+                u"hello", b"world", pytest.raises(AssertionError), marks=py2_only
+            ),
+            pytest.param(
+                u"😊".encode("UTF-8"),
+                b"world",
+                pytest.raises(AssertionError),
+                marks=py2_only,
+            ),
+            pytest.param(
+                u"world",
+                u"😊".encode("UTF-8"),
+                pytest.raises(AssertionError),
+                marks=py2_only,
+            ),
+        ],
+    )
+    def test_handling(self, message, match, expectation):
+        with expectation:
+            with pytest.raises(RuntimeError, match=match):
+                raise RuntimeError(message)