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>
diff --git a/compile_single_file.py b/compile_single_file.py
index bb0a541..eba8e90 100644
--- a/compile_single_file.py
+++ b/compile_single_file.py
@@ -23,7 +23,7 @@
   # to break when we rename directories.
   fingerprints = ['chrome', 'net', 'v8', 'build', 'skia']
   while candidate and not all(
-      [os.path.isdir(os.path.join(candidate, fp)) for fp in fingerprints]):
+      os.path.isdir(os.path.join(candidate, fp)) for fp in fingerprints):
     new_candidate = os.path.dirname(candidate)
     if new_candidate == candidate:
       raise Exception("Couldn't find source-dir from %s" % path)