[Twisted-Python] Python3 twistd daemon for Ubuntu 14.04 alternatives

[Hynek Schlawack]

> As a very simple example: if you have a traditional (non-container) Linux system hosting a Python application in a virtualenv, and you deploy a Python app to a virtualenv e.g. using Puppet or Ansible, you either need to:
> 
> 1. Use no C extensions
> 2. Hope there's a manylinux1 binary wheel
> 3. Use the OS package and --system-site-packages
> 4. Compile the C extensions and make them available to pip
> 
> #2 seems useful now that I know about it but - correct me if I'm wrong - the manylinux1 permitted C dependencies are super-tiny, and would not permit e.g. cryptography or psycopg2?
> 
> #4 is what you are advocating for I believe? But can we agree that for smaller projects, that might seem like a lot of repeated work if the package is already available in the OS repos?

You always say “repeated work” but I hear “small Python script”. :)  We have a few Python projects (not written/maintained by me :)) that did rely on system packages “because it’s easier”.  Guess what!  The other day Ubuntu upgraded PyCrypto (needed Ubuntu Trusty’s ancient Paramiko) under our butts, introduced a regressing and everything blew up: https://www.ubuntu.com/usn/usn-3199-2/ <https://www.ubuntu.com/usn/usn-3199-2/> . That particular project is a virtualenv now too.

The Python build chain got so good on Linux by now that I really don’t even think about C extensions anymore.  Windows is a different story entirely of course. :|

> I'm trying to explain why, based on the efforts we expend locally, it could seem attractive to smaller sites.

Honestly, in the years I’ve been running Python services of different sizes, I have found that distro-provided system packages – unless you are writing software *for* a distribution – are loaded with so many downsides that they’re almost never worth it.  They’re a shortcut and shortcuts usually bite back *eventually*.

—h
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