Unzip a file.gz file.

def gzip_open_to(fin_gz, fout):
    """Unzip a file.gz file."""
    with gzip.open(fin_gz, 'rb') as zstrm:
        with  open(fout, 'wb') as ostrm:
            ostrm.write(zstrm.read())
    assert os.path.isfile(fout), "COULD NOT GUNZIP({G}) TO FILE({F})".format(G=fin_gz, F=fout)
    os.remove(fin_gz)