Port twisted.web.client.HTTPClientFactory to Python 3

[exarkun]

This is the basis of the old web client.

[exarkun]

(In [35999]) Branching to 'webclient-py3-6077'

[itamarst]

(In [36411]) Branching to 'webclient-py3-6077'

[itamarst]

(In [36412]) Move Agent tests into new test module. Refs #6077

[itamarst]

(In [36434]) Branching to 'webclient-py3-6077-2'

[itamar]

 http://buildbot.twistedmatrix.com/boxes-supported?branch=/branches/webclient-py3-6077-2

The code in the new test_agent.py is identical to the tests for Agent that were previously in test_webclient.py, so not much to review there.

[exarkun]

1. Doc for code parameter to Error.__init__ has a typo - bytesing
2. It seems type check for code in Error.__init__ is untested. I deleted it and all the tests still pass. Also I didn't like the look of it, so hopefully it can just be deleted?
3. in client.py, there seems to be a mix of two approaches to formatting bytes:
   • bytes + b'x' + bytes
   • networkString('%sx%s' % (nativeString(bytes), nativeString(bytes))

This isn't really a problem I guess, but it might be nice to decide on one approach and stick to it consistently. If there's some particular reason to prefer one or the other of these in different circumstances, please disregard (but maybe document it on the porting page?)

1. I guess it would be good to have a ticket for dealing with the downloadPage test skips somehow. Delete downloadPage? I forget whether Agent is feature equivalent yet. Or... port downloadPage. And referenced from the code in the typical manner.
2. Blech on testRawSomeCookies :(

That's it. If you can address all these (save the very last point) with nothing too surprising, please merge. Thanks.

[itamar]

1. Fixed.
2. I think that means there's a missing test. It's not exactly important code though, so I'll just chalk it up to the large list of missing test coverage for twisted.web. Deleted.
3. I switched to first format. My gut feeling is "use networkString variant if it's sufficiently complex that it's clearer than lots of addition", which these cases definitely aren't.
4. #6197, added reference.

Left the icky test in, which I think you implied. Plus side, I think we're maybe one feature away (browser-style redirects) from being able to rewrite getPage and downloadPage as wrappers on top of Agent.

[itamarst]

(In [36468]) Address review comments. Refs #6077

[itamarst]

(In [36470]) Merge webclient-py3-6077-2.

Fixes: #6077 Author: itamar Review: exarkun

Port twisted.web.client.getPage to Python 3. Along the way, moved Agent tests into their own test module.