checkstyle: Move from pep8 to pycodestyle

The tool has been renamed in 2016 to make it more obvious what it
is doing. There is no other changes needed on our side.

See https://github.com/PyCQA/pycodestyle/issues/466

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

utils/checkstyle.py

@@ -321,10 +321,10 @@ class Pep8Checker(StyleChecker):
         data = ''.join(self.__content).encode('utf-8')
 
         try:
-            ret = subprocess.run(['pep8', '--ignore=E501', '-'],
+            ret = subprocess.run(['pycodestyle', '--ignore=E501', '-'],
                                  input=data, stdout=subprocess.PIPE)
         except FileNotFoundError:
-            issues.append(StyleIssue(0, None, "Please install pep8 to validate python additions"))
+            issues.append(StyleIssue(0, None, "Please install pycodestyle to validate python additions"))
             return issues
 
         results = ret.stdout.decode('utf-8').splitlines()