Check if GitPython is available and at a compatible version (>= 0.3.0)

def verify_gitpython(self, quiet=False):
        '''
        Check if GitPython is available and at a compatible version (>= 0.3.0)
        '''
        def _recommend():
            if PYGIT2_VERSION and 'pygit2' in self.git_providers:
                log.error(_RECOMMEND_PYGIT2, self.role, self.role)

        if not GITPYTHON_VERSION:
            if not quiet:
                log.error(
                    '%s is configured but could not be loaded, is GitPython '
                    'installed?', self.role
                )
                _recommend()
            return False
        elif 'gitpython' not in self.git_providers:
            return False

        errors = []
        if GITPYTHON_VERSION < GITPYTHON_MINVER:
            errors.append(
                '{0} is configured, but the GitPython version is earlier than '
                '{1}. Version {2} detected.'.format(
                    self.role,
                    GITPYTHON_MINVER,
                    GITPYTHON_VERSION
                )
            )
        if not salt.utils.path.which('git'):
            errors.append(
                'The git command line utility is required when using the '
                '\'gitpython\' {0}_provider.'.format(self.role)
            )

        if errors:
            for error in errors:
                log.error(error)
            if not quiet:
                _recommend()
            return False

        self.opts['verified_{0}_provider'.format(self.role)] = 'gitpython'
        log.debug('gitpython %s_provider enabled', self.role)
        return True