Reads a file which matches the pattern `filename`.

    Args:
        filename The filename pattern

    Returns:
        The file content or the empty string, if the file is not found.

def read_file(filename):
    """Reads a file which matches the pattern `filename`.

    Args:
        filename The filename pattern

    Returns:
        The file content or the empty string, if the file is not found.
    """
    hits = glob.glob('**/{}'.format(filename), recursive=True)
    if not len(hits):
        pf.debug('No file "{}" found.'.format(filename))
        return ''
    elif len(hits) > 1:
        pf.debug('File pattern "{}" ambiguous. Using first.'.format(filename))

    with open(hits[0], 'r') as f:
        return f.read()