'Remove the checksum of the package from the packages checksum file.
This method is called whenever a package is removed from the
repositories in order clean its corresponding checksum.
pkg_name :  The name of the package to be removed'

def remove_checksum(self, pkg_name):

    checksum_dict = self._get_checksum_dict()
    if (pkg_name in checksum_dict):
        del checksum_dict[pkg_name]
    self._save_checksum_dict(checksum_dict)
