Add validation checks in Jurisdiction constructor

[carbonphyber]

Add validation of parameters to Jurisdiction constructor. The constructor now raises Exceptions where it didn't before (BREAKING CHANGE).

This PR prevents all instances of Jurisdiction from working with any hostname other than results.enr.clarityelections.com. This will cause breakage if any downstream users depend on any other hostnames/CNAMEs (potential BREAKING CHANGE). I couldn't find any documentation about Clarify about whether they support such features or not.

This PR also restricts the valid values of level to ['state', 'county', 'city'] (BREAKING CHANGE). Are there any other valid values?

[ghing]

I haven't had a chance to fully think through which values should be accepted, but I think that when doing these checks, it makes more sense to raise a TypeError (when checking whether the URL is string-like) or ValueError (when checking the URL format and the value of level) instead of just Exception.

I also think that checking for strings explicitly is going to cause compatibility problems because there are probably string-like objects that should be supported for which type(url) will not return str. I think it would be more Pythonic to wrap the place where the URL is used as a string in a try/except and to raise a ValueError if the value can't be used as a string. In fact, the functions that are called may already do this and we'd only want to rethrow an error if the existing ValueError message is unclear.

[carbonphyber]

it makes more sense to raise a TypeError (when checking whether the URL is string-like) or ValueError (when checking the URL format and the value of level) instead of just Exception.

Done.

I also think that checking for strings explicitly is going to cause compatibility problems because there are probably string-like objects that should be supported for which type(url) will not return str. I think it would be more Pythonic to wrap the place where the URL is used as a string in a try/except and to raise a ValueError if the value can't be used as a string. In fact, the functions that are called may already do this and we'd only want to rethrow an error if the existing ValueError message is unclear.

I followed your logic and converted the url parameter in the constructor to a str. If that raises, the constructor raises a TypeError. If after that conversion to str doesn't match the URL pattern, we throw a ValueError. Unit tests added for both classes which implement __str__ and classes which don't.

Reraises TypeError, ValueError if thrown in Jurisdiction constructor while converting url to str.

Also worth noting that level now accepts 'precinct' as a valid value for level since a Parser unit test uses it.