I would suggest to *not* create aux/scl_check_erb . But in original check_erb modify the line:
```
-erb -x -T '-' "$F" | ruby -c
+erb -x -T '-' "$F" | /usr/bin/ruby -c
```
and just extend :
```
  sed -ri '1,$s|/usr/bin/ruby|/usr/bin/ruby193-ruby|' upgrade-scripts/* bin/* lib/util/*
```
to 
```
   sed -ri '1,$s|/usr/bin/ruby|/usr/bin/ruby193-ruby|' upgrade-scripts/* bin/* lib/util/* aux/*
```
This is IMO better maintainable.