docs: fix simple typo, raies -> raises

[timgates42]

There is a small typo in ext_tests.py.

Should read raises rather than raies.

Semi-automated pull request generated by
https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md

[coveralls]

Coverage increased (+0.05%) to 65.892% when pulling f8e9bda on timgates42:bugfix_typo_raises into e0b3a9b on stefankoegl:master.

[coveralls]

Coverage remained the same at 65.846% when pulling fb9d0b9 on timgates42:bugfix_typo_raises into e0b3a9b on stefankoegl:master.

[stefankoegl]

That should actually be "does not raise"

[timgates42]

Thanks @stefankoegl fixed it up

[stefankoegl]

Thanks!