style: use new regex match object group access

Author: nedbat

coverage/files.py

@@ -270,7 +270,7 @@ def sep(s):
     """Find the path separator used in this string, or os.sep if none."""
     sep_match = re.search(r"[\\/]", s)
     if sep_match:
-        the_sep = sep_match.group(0)
+        the_sep = sep_match[0]
     else:
         the_sep = os.sep
     return the_sep
@@ -387,7 +387,7 @@ def map(self, path):
         for regex, result in self.aliases:
             m = regex.match(path)
             if m:
-                new = path.replace(m.group(0), result)
+                new = path.replace(m[0], result)
                 new = new.replace(sep(path), sep(result))
                 if not self.relative:
                     new = canonical_filename(new)

coverage/misc.py

@@ -324,17 +324,17 @@ def substitute_variables(text, variables):
 
     def dollar_replace(match):
         """Called for each $replacement."""
-        # Only one of the groups will have matched, just get its text.
+        # Only one of the dollar_groups will have matched, just get its text.
         word = next(g for g in match.group(*dollar_groups) if g)    # pragma: always breaks
         if word == "$":
             return "$"
         elif word in variables:
             return variables[word]
-        elif match.group('strict'):
+        elif match['strict']:
             msg = f"Variable {word} is undefined: {text!r}"
             raise CoverageException(msg)
         else:
-            return match.group('defval')
+            return match['defval']
 
     text = re.sub(dollar_pattern, dollar_replace, text)
     return text