def get_installed_version(vcs):
version_path = _get_version_path(vcs)<EOL>if not os.path.exists(version_path):<EOL><INDENT>raise VersionNotInstalledError<EOL><DEDENT>with open(version_path, '<STR_LIT:r>') as f:<EOL><INDENT>return f.read().strip()<EOL><DEDENT>
Get the installed version for this project.

    Args:
        vcs (easyci.vcs.base.Vcs)

    Returns:
        str - version number

    Raises:
        VersionNotInstalledError