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

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#!/bin/sh

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INKSCAPE=inkscape

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for fname in `ls *.svg`; do

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    for i in `cat $fname |grep -o -e '%%[^%]*%%'|sed 's/%//g'` 

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    do

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        if [ $i.png -nt $fname ]; then

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 	    echo "Skip $i"

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        else

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	    rm  -f $i.png

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	    echo "$INKSCAPE" $fname -z -e $i.png -i $i

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	    "$INKSCAPE" $fname -z -e $i.png -i $i

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        fi

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    done

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done

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cp ico024.png brz.png

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convert -compress none ico*.png brz.ico

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rm -f ico*.png

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convert -compress none poeico*.png poe.ico

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rm -f poeico*.png

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