url: always use str for proxy configuration Previously, proxies didn't work on Python 3 for various reasons. First, the keys to the "proxies" dict are fed into a `setattr(self, "%s_open", ...)` call and passing bytestrings results in setting an oddly named attribute due to the b'' in %s formatting. This resulted in "http_open" and "https_open" not being properly overridden and proxies not being used. Second, the standard library was expecting proxy URLs to be str. And various operations (including our custom code in url.py) would fail to account for the str/bytes mismatch. This commit normalizes everything to str and adjusts our proxy code in url.py to account for the presence of str on Python 3. Differential Revision: https://phab.mercurial-scm.org/D5952

py3: port tinyproxy.py to work with Python 3 There were various str/bytes mismatches in the code. This caused the proxy server to misbehave at run-time. The manifestation was typically premature socket disconnect from the perspective of the client. Differential Revision: https://phab.mercurial-scm.org/D5951

url: always access req._tunnel_host The getattr() was there to handle Python versions before 2.6, which lacked this attribute. We /might/ be able to further delete some code here. However, the behavior here is extremely hard to follow because large parts of this code duplicate code from the Python standard library and it is difficult to understand what is actually needed. Differential Revision: https://phab.mercurial-scm.org/D5950