Add presubmit notice if buganizer bug is malformed

If user enters buganizer bug prefixed with b/, warn user that b: is
expected.

R=apolito@google.com

Bug: 1226474
Change-Id: Ifbced843f9eecc00560cc273ae06bff9d435a815
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3016587
Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Auto-Submit: Josip Sokcevic <sokcevic@google.com>

presubmit_canned_checks.py

@@ -50,7 +50,13 @@ OFF_UNLESS_MANUALLY_ENABLED_LINT_FILTERS = [
 
 def CheckChangeHasBugField(input_api, output_api):
   """Requires that the changelist have a Bug: field."""
-  if input_api.change.BugsFromDescription():
+  bugs = input_api.change.BugsFromDescription()
+  if bugs:
+    if any(b.startswith('b/') for b in bugs):
+      return [
+          output_api.PresubmitNotifyResult(
+              'Buganizer bugs should be prefixed with b:, not b/.')
+      ]
     return []
   else:
     return [output_api.PresubmitNotifyResult(

tests/presubmit_unittest.py

@@ -1993,9 +1993,13 @@ class CannedChecksUnittest(PresubmitTestsBase):
 
   def testCannedCheckChangeHasBugField(self):
     self.DescriptionTest(presubmit_canned_checks.CheckChangeHasBugField,
-                         'Foo\nBUG=1234', 'Foo\n',
-                         presubmit.OutputApi.PresubmitNotifyResult,
-                         False)
+                         'Foo\nBUG=b:1234', 'Foo\n',
+                         presubmit.OutputApi.PresubmitNotifyResult, False)
+
+  def testCannedCheckChangeHasBugFieldWithBuganizerSlash(self):
+    self.DescriptionTest(presubmit_canned_checks.CheckChangeHasBugField,
+                         'Foo\nBUG=b:1234', 'Foo\nBUG=b/1234',
+                         presubmit.OutputApi.PresubmitNotifyResult, False)
 
   def testCannedCheckChangeHasNoUnwantedTags(self):
     self.DescriptionTest(presubmit_canned_checks.CheckChangeHasNoUnwantedTags,