Reformat python files checked by pylint (part 1/2).

After recently changing .pylintrc (see [1]) we discovered that
the presubmit check always checks all the python files when just
one python file gets updated.

This CL moves all these files one step closer to what the linter
wants.

Autogenerated with:

# Added all the files under pylint control to ~/Desktop/to-reformat
cat ~/Desktop/to-reformat | xargs sed -i '1i\\'
git cl format --python --full

This is part 1 out of 2. The second part will fix function names and
will not be automated.

[1] - https://webrtc-review.googlesource.com/c/src/+/186664

No-Presubmit: True
Bug: webrtc:12114
Change-Id: Idfec4d759f209a2090440d0af2413a1ddc01b841
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/190980
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32530}
diff --git a/tools_webrtc/ios/generate_umbrella_header.py b/tools_webrtc/ios/generate_umbrella_header.py
index 3549735..4c700a1 100644
--- a/tools_webrtc/ios/generate_umbrella_header.py
+++ b/tools_webrtc/ios/generate_umbrella_header.py
@@ -14,15 +14,20 @@
 
 
 def GenerateUmbrellaHeader():
-  parser = argparse.ArgumentParser(description='Generate umbrella header')
-  parser.add_argument("-o", "--out", type=str, help="Output file.")
-  parser.add_argument("-s", "--sources", default=[], type=str, nargs='+',
-                      help="Headers to include.")
+    parser = argparse.ArgumentParser(description='Generate umbrella header')
+    parser.add_argument("-o", "--out", type=str, help="Output file.")
+    parser.add_argument("-s",
+                        "--sources",
+                        default=[],
+                        type=str,
+                        nargs='+',
+                        help="Headers to include.")
 
-  args = parser.parse_args()
+    args = parser.parse_args()
 
-  with open(args.out, "w") as outfile:
-    outfile.write(textwrap.dedent("""\
+    with open(args.out, "w") as outfile:
+        outfile.write(
+            textwrap.dedent("""\
     /*
      *  Copyright %d The WebRTC project authors. All Rights Reserved.
      *
@@ -33,11 +38,11 @@
      *  be found in the AUTHORS file in the root of the source tree.
      */\n\n""" % datetime.datetime.now().year))
 
-    for s in args.sources:
-      outfile.write("#import <WebRTC/{}>\n".format(os.path.basename(s)))
+        for s in args.sources:
+            outfile.write("#import <WebRTC/{}>\n".format(os.path.basename(s)))
 
-  return 0
+    return 0
 
 
 if __name__ == '__main__':
-  sys.exit(GenerateUmbrellaHeader())
+    sys.exit(GenerateUmbrellaHeader())