gitsm failed to fetch from remote repo.
Step to reproduce
1. clone poky
2. source oe-init-build-env
3. oe-selftest -r devtool.DevtoolAddTests.test_devtool_add_fetch_git

2018-11-02 15:31:39,728 - oe-selftest - INFO - ======================================================================
2018-11-02 15:31:39,729 - oe-selftest - INFO - FAIL: devtool.DevtoolAddTests.test_devtool_add_fetch_git (subunit.RemotedTestCase)
2018-11-02 15:31:39,729 - oe-selftest - INFO - ----------------------------------------------------------------------
2018-11-02 15:31:39,729 - oe-selftest - INFO - testtools.testresult.real._StringException: Traceback (most recent call last):
  File "/home/ab/yocto-worker/nightly-oe-selftest/build/meta/lib/oeqa/core/decorator/__init__.py", line 32, in wrapped_f
    return func(*args, **kwargs)
  File "/home/ab/yocto-worker/nightly-oe-selftest/build/meta/lib/oeqa/selftest/cases/devtool.py", line 470, in test_devtool_add_fetch_git
    result = runCmd('devtool add %s %s -f "%s" -V 1.5' % (testrecipe, srcdir, url_rev))
  File "/home/ab/yocto-worker/nightly-oe-selftest/build/meta/lib/oeqa/utils/commands.py", line 191, in runCmd
    raise AssertionError("Command '%s' returned non-zero exit status %d:\n%s" % (command, result.status, exc_output))
AssertionError: Command 'devtool add mraa /tmp/devtoolqa0p23zhp9/mraa -f "gitsm://git.yoctoproject.org/mraa;rev=ae127b19a50aa54255e4330ccfdd9a5d058e581d" -V 1.5' returned non-zero exit status 1:
NOTE: Starting bitbake server...
WARNING: -f/--fetch option is deprecated - you can now simply specify the URL to fetch as a positional argument instead
NOTE: Starting bitbake server...
NOTE: Fetching gitsm://git.yoctoproject.org/mraa;rev=ae127b19a50aa54255e4330ccfdd9a5d058e581d;nobranch=1...
Loading cache...done.