Leo P. Singer authored Oct 10, 2019 and Leo P. Singer committed Dec 03, 2019

This fixes the following warning that appears when you run
`python setup.py test`:

```
=============================== warnings summary ===============================
ligo/gracedb/rest.py:1203
  /Users/lpsinger/src/gracedb-client/ligo/gracedb/rest.py:1203: DeprecationWarning: invalid escape sequence \
    """  # noqa: W605

ligo/gracedb/rest.py:1300
  /Users/lpsinger/src/gracedb-client/ligo/gracedb/rest.py:1300: DeprecationWarning: invalid escape sequence \
    """  # noqa: W605

ligo/gracedb/rest.py:2227
  /Users/lpsinger/src/gracedb-client/ligo/gracedb/rest.py:2227: DeprecationWarning: invalid escape sequence \
    """  # noqa: W605

-- Docs: https://docs.pytest.org/en/latest/warnings.html
================ 488 passed, 98 deselected, 3 warnings in 5.63s ================
```