Ensure all config environment vars are correctly exported
Ensure all config environment vars are correctly exported

This is based on a neat trick/nasty hack from David Winterbottom:
https://twitter.com/codeinthehole/status/1063413713892446208

It is the more general fix for the issue addressed in #1191.

annapowellsmith/openpresc,annapowellsmith/openpresc,annapowellsmith/openpresc,annapowellsmith/openpresc,ebmdatalab/openprescribing,ebmdatalab/openprescribing,ebmdatalab/openprescribing,ebmdatalab/openprescribing