Add ability for triggers to be disabled

Will be used in the followup commit to automatically disable broken triggers

endpoints/api/build.py

@@ -22,7 +22,8 @@ from endpoints.api import (RepositoryParamResource, parse_args, query_param, nic
                            require_repo_read, require_repo_write, validate_json_request,
                            ApiResource, internal_only, format_date, api, path_param,
                            require_repo_admin, abort, disallow_for_app_repositories)
-from endpoints.building import start_build, PreparedBuild, MaximumBuildsQueuedException
+from endpoints.building import (start_build, PreparedBuild, MaximumBuildsQueuedException,
+                                BuildTriggerDisabledException)
 from endpoints.exception import Unauthorized, NotFound, InvalidRequest
 from util.names import parse_robot_username
 
@@ -69,6 +70,8 @@ def trigger_view(trigger, can_read=False, can_admin=False, for_build=False):
 
       'config': build_trigger.config if can_admin else {},
       'can_invoke': can_admin,
+      'enabled': trigger.enabled,
+      'disabled_reason': trigger.disabled_reason.name if trigger.disabled_reason else None,
     }
 
     if not for_build and can_admin and trigger.pull_robot:
@@ -309,6 +312,8 @@ class RepositoryBuildList(RepositoryParamResource):
       build_request = start_build(repo, prepared, pull_robot_name=pull_robot_name)
     except MaximumBuildsQueuedException:
       abort(429, message='Maximum queued build rate exceeded.')
+    except BuildTriggerDisabledException:
+      abort(400, message='Build trigger is disabled')
 
     resp = build_status_view(build_request)
     repo_string = '%s/%s' % (namespace, repository)