You forgot to add `` at the end of the line. This causes the following failure at Travis:
```
Warning, treated as error:

/home/travis/build/sympy/sympy/sympy/ntheory/residue_ntheory.py:docstring of sympy.ntheory.residue_ntheory.is_nthpow_residue:5: WARNING: Inline literal start-string without end-string.
```