If installed in an anaconda directory, upgrade conda packages.

def _update_conda_packages():
    """If installed in an anaconda directory, upgrade conda packages.
    """
    conda_bin = _get_conda_bin()
    channels = _get_conda_channels(conda_bin)
    assert conda_bin, ("Could not find anaconda distribution for upgrading bcbio.\n"
                       "Using python at %s but could not find conda." % (os.path.realpath(sys.executable)))
    req_file = "bcbio-update-requirements.txt"
    if os.path.exists(req_file):
        os.remove(req_file)
    subprocess.check_call(["wget", "-O", req_file, "--no-check-certificate", REMOTES["requirements"]])
    subprocess.check_call([conda_bin, "install", "--quiet", "--yes"] + channels +
                          ["--file", req_file])
    if os.path.exists(req_file):
        os.remove(req_file)
    return os.path.dirname(os.path.dirname(conda_bin))