hgweb: use a capped reader for WSGI input stream Per PEP 3333, the input stream from WSGI should respect EOF and prevent reads past the end of the request body. However, not all WSGI servers guarantee this. Notably, our BaseHTTPServer based built-in HTTP server doesn't. Instead, it exposes the raw socket and you can read() from it all you want, getting the connection in a bad state by doing so. We have a "cappedreader" utility class that proxies a file object and prevents reading past a limit. This commit converts the WSGI input stream into a capped reader when the input length is advertised via Content-Length headers. "cappedreader" only exposes a read() method. PEP 3333 states that the input stream MUST also support readline(), readlines(hint), and __iter__(). However, since our WSGI application code only calls read() and since we're not manipulating the stream exposed by the WSGI server, we're not violating the spec here. Differential Revision: https://phab.mercurial-scm.org/D2768

hgweb: document continuereader Differential Revision: https://phab.mercurial-scm.org/D2767

hgweb: remove wsgirequest.__iter__ This was added in d0db3462d568 in 2006. I can't find a justification for this method in PEP 3333. I suspect we were originally intending to use this type as the WSGI application (which should be iterable)? The tests all pass without this method. So let's nuke it. Differential Revision: https://phab.mercurial-scm.org/D2749

hgweb: remove wsgirequest.read() This was just a proxy to self.inp.read(). This method serves little value. Let's nuke it. Callers in the wire protocol server have been updated accordingly. Differential Revision: https://phab.mercurial-scm.org/D2748

hgweb: remove unused methods on wsgirequest writelines() isn't used in our code base. close() was a no-op. It is an optional method per PEP 3333. My eventual goal is to kill the wsgirequest class, hence why I'm removing code. Differential Revision: https://phab.mercurial-scm.org/D2747

wireprotoserver: remove unused argument from _handlehttperror() Differential Revision: https://phab.mercurial-scm.org/D2746