[blinkpy] Call //third_party/depot_tools/luci-auth

Instead of relying on PATH, we explicitly call the luci-auth binary
(or luci-auth.bat on Windows) in blinkpy.

Bug: 1017404
Change-Id: Ic44afadad52d17370db4ada910d6c02e37a95289
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1879559Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709463}

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

@@ -7,13 +7,18 @@
 The main usage is to get the OAuth access token for the service account on LUCI.
 """
 
+from blinkpy.common.path_finder import PathFinder
 
 class LuciAuth(object):
 
     def __init__(self, host):
         self._host = host
+        finder = PathFinder(host.filesystem)
+        luci_auth_bin = 'luci-auth.bat' if host.platform.is_win() else 'luci-auth'
+        self._luci_auth_path = host.filesystem.join(
+            finder.depot_tools_base(), luci_auth_bin)
 
     def get_access_token(self):
         # ScriptError will be raised if luci-auth fails.
-        output = self._host.executive.run_command(['luci-auth', 'token'])
+        output = self._host.executive.run_command([self._luci_auth_path, 'token'])
         return output.strip()

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

+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import unittest
+
+from blinkpy.common.host_mock import MockHost
+from blinkpy.common.net.luci_auth import LuciAuth
+
+
+class LuciAuthTest(unittest.TestCase):
+    def test_run_on_linux(self):
+        host = MockHost(os_name='linux')
+        host.filesystem.maybe_make_directory(
+            '/mock-checkout/third_party/depot_tools')
+
+        luci_auth = LuciAuth(host)
+        luci_auth.get_access_token()
+        self.assertListEqual(
+            host.executive.calls,
+            [['/mock-checkout/third_party/depot_tools/luci-auth', 'token']])
+
+    def test_run_on_windows(self):
+        host = MockHost(os_name='win')
+        host.filesystem.maybe_make_directory(
+            '/mock-checkout/third_party/depot_tools')
+
+        luci_auth = LuciAuth(host)
+        luci_auth.get_access_token()
+        self.assertEqual(
+            host.executive.calls,
+            [['/mock-checkout/third_party/depot_tools/luci-auth.bat', 'token']])