Bug#787009: please add lintian warnings to prepare removing bash as an essential package

[Matthias Klose <doko@debian.org>]

Package: lintian

Bash is still marked as essential while not providing the system shell anymore.
 Before removing this attribute (probably not for the stretch release),
additional build dependencies and dependencies on bash need to be introduced.

 - bash needed for a binary package. that usually means that
   /bin/bash is used as a shebang, or bash is used to start
   shell scripts.

 - bash needed for the source build. Means, that SHELL is set
   in the rules file to /bin/bash, bash is used in any packaging
   scripts, or bash is required in the upstream build system.
   The former too could be checked by lintian, the latter one
   maybe could be checked by the build log checker.

 - adjust the lintian warning, that bash is allowed as a build
   dependency and a dependency, while still being essential.

Reading policy 3.8, I don't see anything which would be needed as a policy change.

Matthias