Wrong instructions for Debian, result in error

[Miloš Jovanović]

Since the present version of Debian is Stretch, following the instructions in the user manual leads to the following error:

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
seafile-gui : Depends: libssl1.0.0 (>= 1.0.0) but it is not installable
Depends: ccnet (>= 5.1.2)
Depends: seafile-daemon (>= 5.1.2) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

There is no present seafile-client for Stretch, see #936. I think the manual should be updated to indicate that seafile-client is not available for the current stable Debian, until that bug is fixed.