Do index conversion for Match.group argument

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/unittest_tags/test_re.txt

@@ -45,6 +45,7 @@
 *graalpython.lib-python.3.test.test_re.ReTests.test_enum
 *graalpython.lib-python.3.test.test_re.ReTests.test_error
 *graalpython.lib-python.3.test.test_re.ReTests.test_flags
+*graalpython.lib-python.3.test.test_re.ReTests.test_group
 *graalpython.lib-python.3.test.test_re.ReTests.test_group_name_in_exception
 *graalpython.lib-python.3.test.test_re.ReTests.test_groupdict
 *graalpython.lib-python.3.test.test_re.ReTests.test_ignore_case

graalpython/lib-graalpython/_sre.py

@@ -191,10 +191,12 @@ def __getitem__(self, item):
 
     def __groupidx(self, idx):
         try:
-            if isinstance(idx, str):
+            if hasattr(idx, '__index__'):
+                int_idx = int(idx)
+                if 0 <= int_idx < self.__compiled_regex.groupCount:
+                    return int_idx
+            else:
                 return self.__compiled_regex.groups[idx]
-            elif 0 <= idx < self.__compiled_regex.groupCount:
-                return idx
         except Exception:
             pass
         raise IndexError("no such group")