--- a/taskcluster/taskgraph/kind/legacy.py
+++ b/taskcluster/taskgraph/kind/legacy.py
@@ -19,17 +19,16 @@ from functools import partial
 from mozpack.path import match as mozpackmatch
 from slugid import nice as slugid
 from taskgraph.util.legacy_commit_parser import parse_commit
 from taskgraph.util.time import (
     json_time_from_now,
     current_json_time,
 )
 from taskgraph.util.templates import Templates
-import taskcluster_graph.build_task
 from taskgraph.util.docker import docker_image
 
 
 ROOT = os.path.dirname(os.path.realpath(__file__))
 GECKO = os.path.realpath(os.path.join(ROOT, '..', '..', '..'))
 # TASKID_PLACEHOLDER is the "internal" form of a taskid; it is substituted with
 # actual taskIds at the very last minute, in get_task_definition
 TASKID_PLACEHOLDER = 'TaskLabel=={}'
@@ -246,16 +245,41 @@ def decorate_task_json_routes(task, json
     :param parameters: dictionary of parameters to use in route templates
     """
     routes = task.get('routes', [])
     for route in json_routes:
         routes.append(route.format(**parameters))
 
     task['routes'] = routes
 
+class BuildTaskValidationException(Exception):
+    pass
+
+def validate_build_task(task):
+    '''The build tasks have some required fields in extra this function ensures
+    they are there. '''
+    if 'task' not in task:
+        raise BuildTaskValidationException('must have task field')
+
+    task_def = task['task']
+
+    if 'extra' not in task_def:
+        raise BuildTaskValidationException('build task must have task.extra props')
+
+    if 'locations' not in task_def['extra']:
+        raise BuildTaskValidationException('task.extra.locations missing')
+
+    locations = task_def['extra']['locations']
+
+    if 'build' not in locations:
+        raise BuildTaskValidationException('task.extra.locations.build missing')
+
+    if 'tests' not in locations and 'test_packages' not in locations:
+        raise BuildTaskValidationException('task.extra.locations.tests or '
+                                           'task.extra.locations.tests_packages missing')
 
 class LegacyKind(base.Kind):
     """
     This kind generates a full task graph from the old YAML files in
     `testing/taskcluster/tasks`.  The tasks already have dependency links.
 
     The existing task-graph generation generates slugids for tasks during task
     generation, so this kind labels tasks using those slugids, with a prefix of
@@ -418,17 +442,17 @@ class LegacyKind(base.Kind):
                                              params['revision_hash'])
                 decorate_task_treeherder_routes(build_task['task'],
                                                 treeherder_route)
                 decorate_task_json_routes(build_task['task'],
                                           json_routes,
                                           build_parameters)
 
             # Ensure each build graph is valid after construction.
-            taskcluster_graph.build_task.validate(build_task)
+            validate_build_task(build_task)
             attributes = build_task['attributes'] = {'kind':'legacy', 'legacy_kind': 'build'}
             if 'build_name' in build:
                 attributes['build_platform'] = build['build_name']
             if 'build_type' in task_extra:
                 attributes['build_type'] = {'dbg': 'debug'}.get(task_extra['build_type'],
                                                                 task_extra['build_type'])
             if build.get('is_job'):
                 attributes['job'] = build['build_name']

--- a/taskcluster/taskgraph/test/test_kind_legacy.py
+++ b/taskcluster/taskgraph/test/test_kind_legacy.py
@@ -1,24 +1,47 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 from __future__ import absolute_import, print_function, unicode_literals
 
 import unittest
 
-from ..kind.legacy import LegacyKind, TASKID_PLACEHOLDER
+from ..kind.legacy import (
+    LegacyKind,
+    TASKID_PLACEHOLDER,
+    validate_build_task,
+    BuildTaskValidationException
+)
 from ..types import Task
 from mozunit import main
 
 
 class TestLegacyKind(unittest.TestCase):
     # NOTE: much of LegacyKind is copy-pasted from the old legacy code, which
     # is emphatically *not* designed for testing, so this test class does not
     # attempt to test the entire class.
 
     def setUp(self):
         self.kind = LegacyKind('/root', {})
 
 
+class TestValidateBuildTask(unittest.TestCase):
+
+    def test_validate_missing_extra(self):
+        with self.assertRaises(BuildTaskValidationException):
+            validate_build_task({})
+
+    def test_validate_valid(self):
+        with self.assertRaises(BuildTaskValidationException):
+            validate_build_task({
+                'extra': {
+                    'locations': {
+                        'build': '',
+                        'tests': ''
+                    }
+                }
+            })
+
+
 if __name__ == '__main__':
     main()

deleted file mode 100644
--- a/testing/taskcluster/taskcluster_graph/build_task.py
+++ /dev/null
@@ -1,34 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this file,
-# You can obtain one at http://mozilla.org/MPL/2.0/.
-
-# This module contains logic related to build tasks
-
-class BuildTaskValidationException(Exception):
-    pass
-
-# XXX: Consider using JSON Schema here like we do elsewhere...
-def validate(task):
-    '''
-    The build tasks have some required fields in extra this function ensures
-    they are there.
-    '''
-    if 'task' not in task:
-        raise BuildTaskValidationException('must have task field')
-
-    task_def = task['task']
-
-    if 'extra' not in task_def:
-        raise BuildTaskValidationException('build task must have task.extra props')
-
-    if 'locations' not in task_def['extra']:
-        raise BuildTaskValidationException('task.extra.locations missing')
-
-    locations = task_def['extra']['locations']
-
-    if 'build' not in locations:
-        raise BuildTaskValidationException('task.extra.locations.build missing')
-
-    if 'tests' not in locations and 'test_packages' not in locations:
-        raise BuildTaskValidationException('task.extra.locations.tests or '
-                                           'task.extra.locations.tests_packages missing')

deleted file mode 100755
--- a/testing/taskcluster/tests/test_build_task.py
+++ /dev/null
@@ -1,30 +0,0 @@
-#!/usr/bin/env python
-
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this file,
-# You can obtain one at http://mozilla.org/MPL/2.0/.
-
-import unittest
-import mozunit
-import taskcluster_graph.build_task as build_task
-
-class TestBuildTask(unittest.TestCase):
-
-    def test_validate_missing_extra(self):
-        with self.assertRaises(build_task.BuildTaskValidationException):
-            build_task.validate({})
-
-    def test_validate_valid(self):
-        with self.assertRaises(build_task.BuildTaskValidationException):
-            build_task.validate({
-                'extra': {
-                    'locations': {
-                        'build': '',
-                        'tests': ''
-                    }
-                }
-            })
-
-if __name__ == '__main__':
-    mozunit.main()
-