This is basically a contrived way of adding a `Recommends` on `libpq5`, to fix #5653.

The way this is supposed to happen in debhelper is to run
`dh_shlibdeps`, which in turn runs `dpkg-shlibdeps`, which spits things out
into `debian/<package>.substvars` whence they can later be included by
`control`.

Previously, we had disabled `dh_shlibdeps`, mostly because `dpkg-shlibdeps`
gets confused about PIL's interdependent objects, but that's not really the
right thing to do and there is another way to work around that.

Since we don't always use postgres, we don't necessarily want a hard Depends on
libpq5, so I've actually ended up adding an explicit invocation of
`dpkg-shlibdeps` for `psycopg2`.

I've also updated the build-depends list for the package, which was missing a
couple of entries.

Signed-off-by: Silke Hofstra <silke@slxh.eu>

This reverts commit c31e375a.

Make sure that users' changes to the config files are preserved.

Fixes #4440.

* implement `reload` by sending the HUP signal

According to the 0.99 release info* synapse now uses the HUP signal to reload certificates:

> Synapse will now reload TLS certificates from disk upon SIGHUP. (#4495, #4524)

So the matrix-synapse.service unit file should include a reload directive.

Signed-off-by: Дамјан Георгиевски <gdamjan@gmail.com>

Rather than hardcoding a config which we always forget to update, generate it
from the default config.

In the debian package, make the virtualenv symlink python to /usr/bin/python3.X
rather than /usr/bin/python3. Also make sure we depend on the right python3.x
package.

This might help a bit with subtle failures when people install a package from
the wrong distro (https://github.com/matrix-org/synapse/issues/4431).

* remove dh_params and set better cipher string

turns out that 0.34.1.1+1 comes before 0.34.1.1+bionic (etc).

The version may only contain "~ 0-9 A-Z a-z + - ." (sorting in that order).

Option 1: replace "+" with something that sorts after +. Options are "-" (but
dpkg-source complains about that) or "." (but that would mean we couldn't
distinguish packaging-only changes from real changes).

Option 2: stick with + and just find something that sorts after 'xenial'. The
only options there are "-", "." (same problems as before), "z", and "+".

Hence, ++1. Sorry.

Otherwise people can't upgrade from matrix-synapse without removing it first

...  to allow installation alongside our matrix-synapse transitional package.

Make sure we don't put the _trial_temp directory in the package target
directory.

Fixes https://github.com/matrix-org/synapse/issues/4322

since #4298, the optional dependencies are no longer installed with a simple
`pip install .`, which meant that they were not being included in the debian
package.

The easy fix to that is dh_virtualenv --extras, but that needs dh_virtualenv
1.1...