replaced several string.format with f-strings

updated tracewin_errorstudy to python3
corrected errors from black/flake8

fix minor issue in DTL_CEL class

some minor cleaning as well

Supporting python 3.8 as well
adding missing field maps for tests
version checker added
version checker needs all deps installed

updated style
fix in lib_tw, was catching the wrong type of error
adding some tests for lib_tw

correcting the amount of data per step in v11 Density_PAR?

Thanks to Ibon for finding this

and over to documentation pages.

we do not support python 2 anymore

fieldmap already documented this way