App Version: 60.0.3112.71 beta
iOS Version: 10.2.1
Device:  iPhone

Steps to reproduce:
Start Appium server locally
Run a franky test using the command below
franky --appium-command NONE --appium-dir-path NONE --use-prebuilt-wda --xcconfig ~/FRANKY/xcconfig.cfg Canary IOS

Observed results:
Test Pass, and this error is presented at the end

*** Running Test Suite with name Canary_Install ***


 >>> Starting test with description  (Test No. 1) First Run UI Flow
> Assuming Appium Server is already running. NOT starting it.
*** Remove, Install and Launch Chrome
*** Tap Accept and continue.
> Assuming Appium Server is already running. NOT starting it.
*** Skip Login
.
----------------------------------------------------------------------
Ran 1 test in 101.193s

OK
Traceback (most recent call last):
  File "/Users/shbarezer/FRANKY/franky_data/bin/franky", line 7, in <module>
    franky.runner.main()
  File "/Users/shbarezer/.vpython/d4c3f3/lib/python2.7/site-packages/franky/runner.py", line 384, in main
    args.no_retry, platform, verbose)
  File "/Users/shbarezer/.vpython/d4c3f3/lib/python2.7/site-packages/franky/runner.py", line 260, in _RunTestSuite
    appium_driver_util.KillAppiumServer(driver_provider_instance._appium_process)
  File "/Users/shbarezer/.vpython/d4c3f3/lib/python2.7/site-packages/franky/appium_util/appium_driver_util.py", line 163, in KillAppiumServer
    if _IsProcessRunning(appium_process.pid):
AttributeError: 'NoneType' object has no attribute 'pid'

Expected results: 
No error at the end of the test.

Note: If the Appium server started via Franky then there is no failures at the end of the test.