Port twisted.web.resource to Python 3

[exarkun]

The basis of the resource publishing model for the Twisted Web server.

[exarkun]

(In [36108]) Branching to 'resource-py3-6078'

[exarkun]

Basically done, I think, except:

1. depends on prefixedMethodNames (#6100)
2. I threw some encode('ascii') and decode('ascii') in. They get the job done in the naive case, but maybe they merit some additional error handling code? Or something? Or maybe 'latin-1' is a better charset to use. Also, maybe they suck for the Python 2 case - time for another string type/compat helper?

Maybe other stuff is terrible about this too, but those stand out to me.

[exarkun]

Still depends on #6100 being resolved first.

[itamar]

Nice to see extra tests.

1. I'm fine with HTTP methods being ASCII only (latin-1 doesn't make sense to me; I suppose it's possible RFC will be expanded to be UTF-8 someday, but not that). For the decode case, nativeString is what you want to use, I believe; in particular since on Python 2 this is a slightly more expensive way of doing what the current trunk code does, so no change or potential for new errors. For the encode... we could create nativeStringToBytes? I suppose if we find another instance where this is necessary we should create it, but for now I'd say just leave it as is.
2. Resource and IResource could use some addition and clarification of the types of parameters. E.g. IResource doesn't mention types at all, and Resource says string when it means bytes.
3. Resource.getChild code example should indicate bytes, likewise putChild.
4. Add the byteness of path elements to the porting howto.

Fix the above, then merge (after #6100 I guess).

[exarkun]

(In [36145]) Fixes to string types used by ErrorPage-related code.

refs #6078

[exarkun]

(In [36147]) Branching to 'resource-py3-6078-2'

[exarkun]

I'm fine with HTTP methods being ASCII only (latin-1 doesn't make sense to me; I suppose it's possible RFC will be expanded to be UTF-8 someday, but not that). For the decode case, nativeString is what you want to use, I believe; in particular since on Python 2 this is a slightly more expensive way of doing what the current trunk code does, so no change or potential for new errors. For the encode... we could create nativeStringToBytes? I suppose if we find another instance where this is necessary we should create it, but for now I'd say just leave it as is.

Switched to nativeString and added a comment for the encode case in r36142.

Resource and IResource could use some addition and clarification of the types of parameters. E.g. IResource doesn't mention types at all, and Resource says string when it means bytes. Resource.getChild code example should indicate bytes, likewise putChild.

Fixed in r36143.

Add the byteness of path elements to the porting howto.

Did that in r36144.

Also fixed some ErrorPage stuff in r36145 and r36146.

[exarkun]

(In [36151]) Merge resource-py3-6078-2

Author: exarkun Reviewer: itamarst Fixes: #6078

Port twisted.web.error and twisted.web.resource to Python 3. Also add some unit tests for twisted.web.resource.Resource which were previously missing.