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.