See: !82 (comment 58149)
See: https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html

- Detect the presence of Python 3.7 and error out correctly if it is not
  available
- Enforce using the correct Python executable for generator.py

png.py module is from PyPNG library
https://github.com/drj11/pypng

* use f-strings
* use `subprocess` and `shutil` instead of `os.system`
* use `enumerate` instead of `range(len)`
* remove unused functions
* deduplicate code

Jan Ziak authored 2 years ago and Arkadiy Illarionov committed 2 years ago

Explanation:

- There is no Makefile rule to re-generate the deleted 'themerc' files
- The themerc files are committed to the git repository

This commit finally fixes distcheck target and ensures that all files
generated as part of build process are later cleaned up.

Signed-off-by: Mateusz Gozdek <mgozdekof@gmail.com>

In case of out-of-source builds, themerc is not part of working
directory but it's in the source directory, so it must be copied from
there. XPM files remains in working directory, as they are generated
using generator.py script.

Part of the effort of fixing distcheck target.

Signed-off-by: Mateusz Gozdek <mgozdekof@gmail.com>

As when doing out-of-source builds, generator.py file won't be present
in the working directory, only Makefile.

Part of effort on fixing distcheck target.

Signed-off-by: Mateusz Gozdek <mgozdekof@gmail.com>

As they will be used during build process to generate XPM and PNG files
and later copied to the distro package.

Part of efforts for fixing distcheck target.

Signed-off-by: Mateusz Gozdek <mgozdekof@gmail.com>

Signed-off-by: Mateusz Gozdek <mgozdekof@gmail.com>