Revert "Use pylint 2.7 for depot_tools"

This reverts commit 22bf605bb63f8ff01aa7c1a2841718e3489b43d6.

Reason for revert: breaks gclient sync

Original change's description:
> Use pylint 2.7 for depot_tools
>
> This includes a few fixes for specific errors, and disables several new
> warnings introduced in this version, in order to allow for an incremental migration.
>
> Bug:1262286
> Change-Id: Ie97d686748c9c952e87718a65f401c5f6f80a5c9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3400616
> Reviewed-by: Gavin Mak <gavinmak@google.com>
> Commit-Queue: Aravind Vasudevan <aravindvasudev@google.com>

Bug: 1262286
Change-Id: Ieb946073c7886c7bf056ce843a5a48e82becf7a5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3413672
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
diff --git a/gerrit_util.py b/gerrit_util.py
index 429e1de..4d5e78b 100644
--- a/gerrit_util.py
+++ b/gerrit_util.py
@@ -254,8 +254,8 @@
       if a[0]:
         secret = base64.b64encode(('%s:%s' % (a[0], a[2])).encode('utf-8'))
         return 'Basic %s' % secret.decode('utf-8')
-
-      return 'Bearer %s' % a[2]
+      else:
+        return 'Bearer %s' % a[2]
     return None
 
   def get_auth_email(self, host):
@@ -696,8 +696,7 @@
     jmsg = GetChangeRevisions(host, change)
     if not jmsg:
       return None
-
-    if len(jmsg) > 1:
+    elif len(jmsg) > 1:
       raise GerritError(200, 'Multiple changes found for ChangeId %s.' % change)
     revision = jmsg[0]['current_revision']
   path = 'changes/%s/revisions/%s/review'
@@ -982,8 +981,7 @@
   if not jmsg:
     raise GerritError(
         200, 'Could not get review information for change "%s"' % change)
-
-  if jmsg[0]['current_revision'] != revision:
+  elif jmsg[0]['current_revision'] != revision:
     raise GerritError(200, 'While resetting labels on change "%s", '
                    'a new patchset was uploaded.' % change)
 
@@ -1002,7 +1000,7 @@
   """
   path = 'changes/'
   body = {'project': project, 'branch': branch, 'subject': subject}
-  body.update(dict(params))
+  body.update({k: v for k, v in params})
   for key in 'project', 'branch', 'subject':
     if not body[key]:
       raise GerritError(200, '%s is required' % key.title())