failed test without installed diskimage-builder

[dshkuratov]

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
dibctl/dib.py:34: in validate_version
    dib_version = get_installed_version()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    def get_installed_version():
        try:
            version = pkg_resources.get_distribution('diskimage_builder').version
        except pkg_resources.DistributionNotFound:
>           raise NoDibError("diskimage-builder is not available (as python package)")
E           NoDibError: diskimage-builder is not available (as python package)

[amarao]

In version 1.x all actual interaction with diskimage builder is in integration_test/ . Unit tests should pass without them.