Possibly fix "maintainer-shell-script-fails-syntax-check" message

Cause is cryptic, but could be due to the shebang:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=478192
7 jobs for fix/ancient-standards in 2 minutes and 8 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #4155
build-deb:buster

00:01:30

passed #4153
build-deb:jessie

00:01:25

passed #4154
build-deb:stretch

00:01:46

 
  Test
failed #4158
test-deb:buster

00:00:19

failed #4156
test-deb:jessie

00:00:21

failed #4157
test-deb:stretch

00:00:21

 
  Deploy
skipped #4159
aptly
 
Name Stage Failure
failed
test-deb:stretch Test
Setting up nginx (1.17.0-2~eth) ...
/var/lib/dpkg/info/nginx.postinst: line 7: unexpected EOF while looking for matching `"'
dpkg: error processing package nginx (--install):
subprocess installed post-installation script returned error exit status 2
Errors were encountered while processing:
nginx
Running after script...

ERROR: Job failed: exit code 1
failed
test-deb:jessie Test
/var/lib/dpkg/info/nginx.postinst: line 7: unexpected EOF while looking for matching `"'
dpkg: error processing package nginx (--install):
subprocess installed post-installation script returned error exit status 2
Processing triggers for systemd (215-17+deb8u13) ...
Errors were encountered while processing:
nginx
Running after script...

ERROR: Job failed: exit code 1
failed
test-deb:buster Test
Setting up nginx (1.17.0-2~eth) ...
/var/lib/dpkg/info/nginx.postinst: line 7: unexpected EOF while looking for matching `"'
dpkg: error processing package nginx (--install):
installed nginx package post-installation script subprocess returned error exit status 2
Errors were encountered while processing:
nginx
Running after script...

ERROR: Job failed: exit code 1