def is_numba_installed(raise_error=False):
    """Test if numba is installed."""
    try:
        import numba
        is_installed = True
    except ImportError:
        is_installed = False
    if raise_error and not is_installed:
        raise IOError(
            'numba not installed. See http://numba.pydata.org/ for installation instructions.'
            )
    return is_installed
