executables in lalsuite-6.71 from pypi not working (missing sys import)

@duncanmmacleod @adam-mercer doing the following to install lalsuite-6.71 from pypi into a clean venv

python3 -m venv /home/david.keitel/bin/test-lalsuite-6.71
source /home/david.keitel/bin/test-lalsuite-6.71/bin/activate
pip install --upgrade pip
pip install lalsuite
lalapps_version

I get

Traceback (most recent call last):
  File "/home/david.keitel/bin/test-lalsuite-6.71/bin/lalsim-inspiral", line 10, in <module>
    os.execv(new_path, sys.argv)
NameError: name 'sys' is not defined

and similar for any other lalapps or lalsim executable. Same behaviour on my local machine and on Arcca. With 6.70 it still works.

The error is obviously that there is no explicit import sys in these wrapper scripts, and if I manually hack that into any of them, it seems sufficient to get things running. But I don't know where in the build system they are generated from and what has changed since the last release to break this.

(The pip upgrade is necessary because with the 18.1 I get by default in a fresh venv on both machines, it would just install 6.70, and even a pip install lalsuite==6.71 claims that version doesn't exist, so we seem to have some implicit dependency there, which might also be good to document on the pypi page. Let me know if you'd like a separate issue for that.)