When a regex pattern contains bytes instead of a string use escape_encode to turn it into a string before further processing. Thanks @nicoddemus for the review and tips!

testing/acceptance_test.py

@@ -392,6 +392,20 @@ class TestGeneralUsage:
         monkeypatch.setitem(sys.modules, 'myplugin', mod)
         assert pytest.main(args=[str(tmpdir)], plugins=['myplugin']) == 0
 
+    def test_parameterized_with_bytes_regex(self, testdir):
+        p = testdir.makepyfile("""
+            import re
+            import pytest
+            @pytest.mark.parametrize('r', [re.compile(b'foo')])
+            def test_stuff(r):
+                pass
+        """
+        )
+        res = testdir.runpytest(p)
+        res.stdout.fnmatch_lines([
+            '*1 passed*'
+        ])
+
 
 class TestInvocationVariants:
     def test_earlyinit(self, testdir):

testing/python/metafunc.py

@@ -170,6 +170,11 @@ class TestMetafunc:
         result = idmaker((py.builtin._totext("a"), "b"), [({}, b'\xc3\xb4')])
         assert result == ['a0-\\xc3\\xb4']
 
+    def test_idmaker_with_bytes_regex(self):
+        from _pytest.python import idmaker
+        result = idmaker(("a"), [(re.compile(b'foo'), 1.0)])
+        assert result == ["foo"]
+
     def test_idmaker_native_strings(self):
         from _pytest.python import idmaker
         totext = py.builtin._totext