Reland of PyLint fixes for tools-webrtc and webrtc/tools (patchset #1 id:1 of https://codereview.webrtc.org/2737233003/ )

Reason for revert:
Fixing errors for reland. I have tested that this does not make Chromium video quality tests fail.

Original issue's description:
> Revert of PyLint fixes for tools-webrtc and webrtc/tools (patchset #3 id:40001 of https://codereview.webrtc.org/2736233003/ )
>
> Reason for revert:
> Fails video quality tests in Chrome:  http://build.chromium.org/p/chromium.webrtc.fyi/builders/Win10%20Tester/builds/6568
> I should have looked more closer at those :(
>
> Original issue's description:
> > PyLint fixes for tools-webrtc and webrtc/tools
> >
> > Fix a lot of errors before bringing in the new config in
> > https://codereview.webrtc.org/2737963003/
> >
> > BUG=webrtc:7303
> > NOTRY=True
> >
> > Review-Url: https://codereview.webrtc.org/2736233003
> > Cr-Commit-Position: refs/heads/master@{#17137}
> > Committed: https://chromium.googlesource.com/external/webrtc/+/f5318e1f391859c82aaa47b297429e50f41f6b3c
>
> TBR=oprypin@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:7303
>
> Review-Url: https://codereview.webrtc.org/2737233003
> Cr-Commit-Position: refs/heads/master@{#17142}
> Committed: https://chromium.googlesource.com/external/webrtc/+/94f4d9effc3fa1ee6a6a48a7bbdef6684defd1dc

NOTRY=true
BUG=webrtc:7312

Review-Url: https://codereview.webrtc.org/2741733003
Cr-Commit-Position: refs/heads/master@{#17541}
diff --git a/webrtc/examples/androidtests/video_quality_loopback_test.py b/webrtc/examples/androidtests/video_quality_loopback_test.py
index 5ef8537..7c7ef31 100755
--- a/webrtc/examples/androidtests/video_quality_loopback_test.py
+++ b/webrtc/examples/androidtests/video_quality_loopback_test.py
@@ -89,10 +89,10 @@
 
   ffmpeg_path = os.path.join(toolchain_dir, 'linux', 'ffmpeg')
 
-  def convert_video(input_video, output_video):
+  def ConvertVideo(input_video, output_video):
     _RunCommand([ffmpeg_path, '-y', '-i', input_video, output_video])
 
-  convert_video(test_video, test_video_yuv)
+  ConvertVideo(test_video, test_video_yuv)
 
   reference_video = os.path.join(SRC_DIR,
       'resources', 'reference_video_640x360_30fps.y4m')
@@ -100,7 +100,7 @@
   reference_video_yuv = os.path.join(temp_dir,
       'reference_video_640x360_30fps.yuv')
 
-  convert_video(reference_video, reference_video_yuv)
+  ConvertVideo(reference_video, reference_video_yuv)
 
   # Run compare script.
   compare_script = os.path.join(SRC_DIR, 'webrtc', 'tools',