Exclude pyjslib.py from python3 syntax correction check

pyjs doesn't support python3 and it's unmaintained.
async is a new keyword introduced in python 3.7.

./tests/tools/check_source.sh
Syntax checking using python3 ...
Python 3.7.2+

Syntax error in ./runtime/Worker.py
File "./svgui/pyjs/lib/pyjslib.py", line 24
def import_module(path, parent_module, module_name, dynamic=1, async=False):
^
SyntaxError: invalid syntax

revert occasionally committed changed first_steps project.

project was changed by commit:
update translations from https://www.transifex.com/beremiz/beremiz-ide (756d02cf78db)

Merged in masterschlumpf/beremiz/generate-button (pull request #38)

"Generate Prgram" button

Approved-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>

Create a "Generate Program As..." menu to make the "Generate Program" toolbutton even more useful.

The behaviour is the same as "Save" and "Save As...". Now "Generate Program" uses the last filename
if known and "Generate Progam As..." asks every time.