Fix typo: & -> and

`and` is the boolean operator for AND in [Python][1].
`&` is the bitwise operator for AND in [Python][2].

[1]: https://docs.python.org/2/reference/expressions.html#boolean-operations
[2]: https://docs.python.org/2/reference/expressions.html#binary-bitwise-operations
Merge pull request #8622 from ciupicri/typo

Fix typo: & -> and