Handle non-syntax errors from Ansible

If a playbook refers to a role that does not exist, Ansible will output
"ERROR!" followed by an error. Such as:

  ERROR! the role 'add-launchpadlib-credentials' was not found in ...

  The error appears to have been in '...':
  line 5, column 7, but may be elsewhere in the file depending on the exact syntax problem.

  The offending line appears to be:

    - add-sshkey
    - add-launchpadlib-credentials
      ^
  here

Simply adding the error to the build log will help people track down the
issue.

Change-Id: If49c50c16844243cbbade4b7fef7a43df4107d43
1 file changed