py3: use raw string to query EmailMessage in gnuarch converter

py3: use mail.parsebytes() in gnuarch catlog parser We drop 'catlogparser' attribute now unused.

tests: handle Message-Id line wrapping in test-notify-changegroup.t This fixes this test on Python 3 with a long hostname. See changeset 4128ffba4431 for details.

py3: define and use json.loads polyfill Python 3.5's json.loads() requires a str. Only Python 3.6+ supports passing a bytes or bytearray. This commit implements a json.loads() polyfill on Python 3.5 so that we can use bytes. The added function to detect encodings comes verbatim from Python 3.7.

contrib: require Python 3.6 for byteify-strings.py This script makes use of `token.COMMENT`, which apparently isn't present until Python 3.6. So make the script and its test conditional on Python 3.6.

demandimportpy3: only use lazy extension loader on Python 3.6+ There was an inline comment denoting a bug in the lazy extension loader on Python 3.5 which prevents it from working there. But the code was not conditional on the Python version. The result of this was a myriad of failures on Python 3.5 due to getattr() and friends not working on lazy extension modules. By making extension modules non-lazy on Python 3.5, we reduce the number of test failures from 48 to 22 on that Python version.

ui: flush before prompting for input with readline I was using `hg absorb` with Python 3 and noticed that the prompt was appearing without any output about what would be done. After I answered the prompt, the output was printed to stdout. This appears to be a buffering difference between Python 2 and Python 3. To work around it, this commit adds an explicit flush() before calling the raw input function when readline is used.

histedit: restore hex nodeids to be 12 digits long I accidentally switched from 12 digits to 40 digits while making the code py3-compatible. Thanks to Yuya for noticing. Differential Revision: https://phab.mercurial-scm.org/D7200

tests: fix typo "includfe" Differential Revision: https://phab.mercurial-scm.org/D7180

py3: fix fsmonitor's _watchmantofsencoding exception message encoding Differential Revision: https://phab.mercurial-scm.org/D7190

py3: use native strings as keys into **opts in chistedit Now you should be able to successfully confirm your histedit plan (at least in the case I tried). Even continuing after conflicts and finishing the histedit worked. Differential Revision: https://phab.mercurial-scm.org/D7186

py3: open chistedit file in binary mode using vfs We write bytes to the file, so it should be open in binary mode. Opening it via the vfs takes care of that for us. Now you'll get yet a different traceback if you try to confirm you histedit plan. Differential Revision: https://phab.mercurial-scm.org/D7185

py3: avoid another b''.format() in chistedit Now you'll get a different traceback if you try to confirm you histedit plan. Differential Revision: https://phab.mercurial-scm.org/D7184

py3: render message about conflicts in chistedit code Now you can also reorder commits that (potentially) conflict. Just don't try to confirm the changes yet (because then it crashes). Differential Revision: https://phab.mercurial-scm.org/D7183

py3: handle keypresses in chistedit Now you can navigate and change the action for a commit. You can also reorder commits, as long as that doesn't result in a conflict (then it crashes). Differential Revision: https://phab.mercurial-scm.org/D7182

py3: make chistedit render Now you can see the list of commits, but it crashes when you press a key. Differential Revision: https://phab.mercurial-scm.org/D7181

py3: fix exception display encoding in contrib/simplemerge.py Differential Revision: https://phab.mercurial-scm.org/D7191

py3: fix exception message check in test-linerange.py's testOutOfRange Differential Revision: https://phab.mercurial-scm.org/D7192

py3: fix exception message encoding in scmutil.py's simplekeyvaluefile.read Differential Revision: https://phab.mercurial-scm.org/D7193

py3: fix crecord.py's editpatchwitheditor exception message encoding Differential Revision: https://phab.mercurial-scm.org/D7194

py3: fix exception message encoding in infinitepush Differential Revision: https://phab.mercurial-scm.org/D7195

py3: fix fsmonitor's _handleunavailable exception message encoding Differential Revision: https://phab.mercurial-scm.org/D7196

packaging: update built-in Fedora support to Fedora 31 This is now quite easy ...

packaging: refactor "fedora29" target to a single more generic "fedora" target Fedora moves fast in version numbers, and often with Mercurial packaging being backwards compatible. Also, most people use the system package. There is thus much work and tech debt and little value in providing explicit built-in support for several versions. Thus, only aim for providing built-in support for latest Fedora version, and make it easy to update.

packaging: make dockerrpm fedora target more generic Fedora moves fast in version numbers, and often with Mercurial packaging being backwards compatible. Thus, only aim for providing built-in support for latest Fedora version, and make it easy to update. With this refactoring, 'dockerrpm fedora31' also works. 'dockerrpm fedora' will use the 'fedora:latest' Docker image.

packaging: use "python3" for fedora29 ... and as buildrpm default Change the buidrpm default. The CentOS targets explicitly use "python", and changing the default will only influence Fedora 29. A Python 3 package needs python3 dependencies, so pythonexe (and pythonver) is used for specifying dependencies. Other OS versions will keep using "python" as before ... or potentially change to explicit "python2". Fedora 29 packages can thus also still be built for Python 2 - just not in the docker image that is updated for Python 3.

packaging: use "--python python" for centos7 to avoid explicit "python2" This is a partial backout of 92a51a45d44c. We will need to be able to control whether package dependencies are python2 or python3. Generally (at least in recent Fedora), the package prefix match the name of the python executable ... but CentOS 7 doesn't use the python2 prefix in package name or alias for python-docutils yet, so just keep centos7 in the unversioned "python" world. Change the new (unused) buildrpm "--python3" option (introduced in a6dcac6454c1) to "--python python3" to get a more generic method for explicit control over whether we use python, python2 or python3.

packaging: fix docker-centos5 - use pythonexe and set to "python" as before Fix 92a51a45d44c .