Some packages have undocumented build requirements

[jakint0sh]

After the update to version 2.80.0, glib will now fail to configure (and subsequently fail to build) unless the Python 3 module packaging is installed. This was initially found in #3059.

The module can either be installed with pip or by the apt package python3-packaging.

I feel like this requirement should be added to the documentation. Adding the apt package to the list of requirements in docs/index.html would be good.

[mabrand]

Would you mind making a pull request for this?

[jakint0sh]

I just figured out a similar issue with proj. It needs sqlite3 to be installed on the host system in order to configure and build (apt-get install sqlite3 is sufficient to fix the issue). I will figure out how to add python3-packaging and sqlite3 to the list of requirements that are checked when make check-requirements is run, and add them to docs/index.html as well. I'll open a pull request when this is completed.

[jakint0sh]

Opened a PR #3069. I quickly figured out that 1. Checking if sqlite3 is installed by using the currently in-place infrastructure in the main Makefile doesn't work at all, and 2. There is no infrastructure in place for checking if python modules are installed. Thus I have not added either to the list of things that make check-requirements checks.

I think more infrastructure should be added there, to allow more complex checks to take place (like checking if python modules are installed, which isn't trivial). I may work on this in the future.

I will keep this issue open in case I come across any other build requirements that are not listed anywhere