def requires(filename):
    """Returns a list of all pip requirements

    :param filename: the Pip requirement file (usually 'requirements.txt')
    :return: list of modules
    :rtype: list
    """
    modules = []
    with open(filename, 'r') as pipreq:
        for line in pipreq:
            line = line.strip()
            if line.startswith('#') or not line:
                continue
            modules.append(line)
    return modules