Reland "[blinkpy] Always suppress stderr of git-cl"

This is a reland of 964fde12,
which was reverted at 043d9f87
because of a bug.

This reland fixes the bug by setting optional params correctly
in git_cl.py.

Original change's description:
> [blinkpy] Always suppress stderr of git-cl
>
> * stderr is now always ignored for git-cl (i.e. the optional argument is
>   removed from GitCL.run as no one uses it).
> * Instead of only excluding stderr from the return value, we now throws
>   away stderr completely by redirecting it to DEVNULL so that the logs
>   don't get polluted.
>
> Some drive-by pylint fixes are applied.
>
> Bug: 953499
> Change-Id: I5668576e1cc3dfe2a83a7cafc12a09f4a0029358
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628606
> Auto-Submit: Robert Ma <robertma@chromium.org>
> Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
> Commit-Queue: Robert Ma <robertma@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#663599}

Bug: 953499
Change-Id: Idccc65e089ee67f744411752800f41fd63a93d92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1631765Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663882}

third_party/blink/tools/blinkpy/common/net/git_cl.py

@@ -52,14 +52,11 @@ class GitCL(object):
         self._cwd = cwd
         self._git_executable_name = Git.find_executable_name(host.executive, host.platform)
 
-    def run(self, args, return_stderr=False):
+    def run(self, args):
         """Runs git-cl with the given arguments and returns the output.
 
         Args:
             args: A list of arguments passed to `git cl`.
-            return_stderr: Whether to include stderr in the returned output (the
-                default is False because git-cl will show a warning when running
-                on Swarming bots with local git cache).
 
         Returns:
             A string (the output from git-cl).
@@ -67,7 +64,10 @@ class GitCL(object):
         command = [self._git_executable_name, 'cl'] + args
         if self._auth_refresh_token_json and args[0] in _COMMANDS_THAT_TAKE_REFRESH_TOKEN:
             command += ['--auth-refresh-token-json', self._auth_refresh_token_json]
-        return self._host.executive.run_command(command, cwd=self._cwd, return_stderr=return_stderr)
+        # Suppress the stderr of git-cl because git-cl will show a warning when
+        # running on Swarming bots with local git cache.
+        return self._host.executive.run_command(
+            command, cwd=self._cwd, return_stderr=False, ignore_stderr=True)
 
     def trigger_try_jobs(self, builders, bucket=None):
         """Triggers try jobs on the given builders.

third_party/blink/tools/blinkpy/common/system/executive.py

@@ -311,13 +311,17 @@ class Executive(object):
                     error_handler=None,
                     return_exit_code=False,
                     return_stderr=True,
-                    decode_output=True, debug_logging=True):
+                    ignore_stderr=False,
+                    decode_output=True,
+                    debug_logging=True):
         """Popen wrapper for convenience and to work around python bugs."""
         assert isinstance(args, list) or isinstance(args, tuple)
         start_time = time.time()
 
+        assert not (return_stderr and ignore_stderr)
         stdin, string_to_communicate = self._compute_stdin(input)
-        stderr = self.STDOUT if return_stderr else None
+        stderr = self.STDOUT if return_stderr else (
+            self.DEVNULL if ignore_stderr else None)
 
         process = self.popen(args,
                              stdin=stdin,

third_party/blink/tools/blinkpy/common/system/executive_mock.py

@@ -123,6 +123,7 @@ class MockExecutive(object):
                     error_handler=None,
                     return_exit_code=False,
                     return_stderr=True,
+                    ignore_stderr=False,
                     decode_output=True,
                     debug_logging=True):
         self._append_call(args, cwd=cwd, input=input, env=env)
@@ -156,7 +157,7 @@ class MockExecutive(object):
         output = self._output
         if return_stderr:
             output += self._stderr
-        if decode_output and type(output) is not unicode:
+        if decode_output and not isinstance(output, unicode):
             output = output.decode('utf-8')
 
         return output