[LyX/master] Add new placeholder $${python} to configure

[Pavel Sanda]

On Tue, Jan 04, 2022 at 12:52:37AM +0100, JosĂŠ Matos wrote:
> commit 109ea2be4a21ca93d22ab25703b3352a50fbbe3b
> Author: José Matos <jamatos at lyx.org>
> Date:   Tue Jan 4 00:21:34 2022 +0000
> 
>     Add new placeholder $${python} to configure
>     
>     This ensures that we use a consistent Python interpreter in LyX.
>     
>     $${python} is replaced by the Python version found.
>     
>     Users can apply this in preferences and use the same version defined by
>     LyX.

Hi Jose,

this what I see in curent master:
1. start lyx 
2. load file
3. this is  what I see in terminal window:
env: '$${python}': No such file or directory

Most likely related to image preview conversions, this what I see with debug
messages on graphics:
graphics/PreviewLoader.cpp (757): PreviewLoader::finishedInProgress(127): processing failed for $${python} $$s/scripts/lyxpreview2bitmap.py --png "/tmp/lyx_tmpdir.LiGxsfYQmUxW/lyx_tmpbuf6/lyxpreviewGdodeo.tex" --dpi 115 --fg ff9822 --bg 000000 --bibtex="bibtex"


These binaries available on my system:
python     python2    python2.7  python3    python3.9
python defaults to python2.7

Pavel