Bug#886742: postgresql-9.4-postgis-2.1 missing in stretch

[Juergen Fuchsberger]

Package: postgresql-9.4-postgis-2.1
Severity: critical
Justification: causes serious data loss

Dear Maintainer,

Due to missing postgresql-9.4-postgis-2.1 in stretch, a postgis enabled
database becomes corrupt when upgrading from jessie to stretch since
the required postgis libraries are missing. This can cause serious data
loss, because once upgraded to stretch, the postgis data can't be
accesed nor dumped (Database gives error "could not access file
"$libdir/postgis-2.1": no such file or directory"). 
Also upgrading the database to postgresql-9.6 does not work. 

-- System Information:
Debian Release: 8.10
  APT prefers oldstable-updates
  APT policy: (500, 'oldstable-updates'), (500, 'oldstable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/20 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)