def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def rename_source(self):
        """This is fairly horrible.
        The github tarfiles have weird names that do not correspond to the
        canonical name. We need to rename these, but leave a symlink for
        spack to work with.
        """
        # Note that this particular OpenFOAM requires absolute directories
        # to build correctly!
        parent   = os.path.dirname(self.stage.source_path)
        original = os.path.basename(self.stage.source_path)
        target   = 'OpenFOAM-{0}'.format(self.version)
        # Could also grep through etc/bashrc for WM_PROJECT_VERSION
        with working_dir(parent):
            if original != target and not os.path.lexists(target):
                os.rename(original, target)
                os.symlink(target, original)
                tty.info('renamed {0} -> {1}'.format(original, target))