These are notes regarding packaging of weewx for debian systems.
mwall 09apr2020

For the transition from python2 to python3, we introduce a new package
python3-weewx.  This contains the python3-compatible weewx4 implementation.
Those who need python2 can continue with the weewx packages for as long as
weewx supports python2.

There is one control file for python2 and a different control file for python3.
The primary reason for this is that the dependencies for python2 have different
names from those for python3

It is not possible to have a single weewx installation that will work for both
python2 and python3.  Python ensures that the compiled code will not conflict
(.pyc files for python2 versus __pycache__ directories for python3), however
the weewx entry points have a shebang specifies the python version.

The weewx packaging uses relatively low-level debian packaging tools.  It uses
some of the debhelper python rules.  It does not use the python tools for
creating deb packages.

One reason for this approach is that WeeWX is not just another python package
that is plopped into the python library tree.  WeeWX prefers instead to live
on its own as a standalone application, with everything in a single directory
tree (or in system-specific trees such as /var/lib, /etc).

The packaging process does the following:

1) use setup.py sdist to generate the 'official' source tree (setup.py)
2) expand that source tree into the build space (makefile)
3) copy the parts of the build tree into the debian staging tree (debian/rules)
4) invoke debian packaging tool to create the package (dpkg-buildpackage)

WeeWX was traditionally packaged in a single deb file with this naming:

weewx_x.y.z-n_all.deb

As of 2020, the packaging files now generate two different deb files:

weewx_x.y.z-n_all.deb
python3-weewx_x.y.z-n_all.deb

These packages are identical other than the shebang in the weewx entry points
and the dependencies.


References:

debian python policy:
https://www.debian.org/doc/packaging-manuals/python-policy/

debian library style guide:
https://wiki.debian.org/Python/LibraryStyleGuide

debian pybuild:
https://wiki.debian.org/Python/Pybuild

basic debian lore:
https://www.debian.org/doc/debian-policy/ch-source.html

what does dh_auto do for python?
dh_auto_configure -
dh_auto_build     - ./setup.py build
dh_auto_test      -
dh_auto_install   - ./setup.py install --blah
dh_auto_clean     - ./setup.py clean

override_dh_auto_install:
        ./setup.py install --no-prompt --prefix=build

targets:  clean, binary, binary-arch, binary-indep, build, build-arch, build-indep

useful examples:
https://www.wefearchange.org/2012/01/ebian-package-for-python-2-and-3.html
https://www.v13.gr/blog/?p=412