Fix CheckCIPDManifest for python 3.

Change-Id: Icf7b8e7ad732a731520550ff9e276f13016effb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4149964
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Auto-Submit: Brian Ryner <bryner@google.com>

presubmit_canned_checks.py

@@ -1645,6 +1645,8 @@ def CheckCIPDManifest(input_api, output_api, path=None, content=None):
     assert path is None, 'Cannot provide both "path" and "content".'
     cmd += ['-ensure-file=-']
     kwargs['stdin'] = content
+    if input_api.sys.version_info.major != 2:
+      kwargs['stdin'] = kwargs['stdin'].encode('utf-8')
     # quick and dirty parser to extract checked packages.
     packages = [
       l.split()[0] for l in (ll.strip() for ll in content.splitlines())

tests/presubmit_unittest.py

@@ -3125,7 +3125,7 @@ the current line as well!
         input_api, presubmit.OutputApi, content='manifest_content')
     self.assertEqual(command.cmd,
         ['cipd', 'ensure-file-verify', '-log-level', 'debug', '-ensure-file=-'])
-    self.assertEqual(command.stdin, 'manifest_content')
+    self.assertEqual(command.stdin, b'manifest_content')
     self.assertEqual(command.kwargs, {
         'stdin': subprocess.PIPE,
         'stdout': subprocess.PIPE,
@@ -3151,7 +3151,7 @@ the current line as well!
         })
     self.assertEqual(command.cmd,
         ['cipd', 'ensure-file-verify', '-ensure-file=-'])
-    self.assertEqual(command.stdin, content)
+    self.assertEqual(command.stdin, content.encode())
     self.assertEqual(command.kwargs, {
         'stdin': subprocess.PIPE,
         'stdout': subprocess.PIPE,