kubuntu akonadi server depends on akonadi-backend-mysql, but not akonadi-backend-sqlite

akonadi-server depends on akonadi-backend-mysql, but not akonadi-backend-sqlite.

If a conditional dependency is not possible.
Every backend package should provide a virtual package (e.g. akonadi-backend) and akonadi-server should depend only on the akonadi-backend virtual package and the user should be able to choose whatever backend it wants. (mysql, sqlite, postgresql)

In order to install kmail, for example, the full mysql workhorse has to be installed in a user machine. The mais issue, is the need to have mysql-community-server-core in the users machine!

Also note that installing akonadi-backend-mysql, apt can install kmail fine. So there is some apt bug involved.

apt = 1.8.3
and using kubuntu backports ppa updated in october, 04.

---------------8<-------------------
# apt-get install kmail
Reading package lists... Done
Building dependency tree
Reading state information... Done
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:
 kmail : Depends: akonadi-server (>= 4:16.04) but it is not going to be installed
         Depends: kdepim-runtime but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

# apt-get install akonadi-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
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:
 akonadi-server : Depends: akonadi-backend-mysql (= 4:18.12.3-0ubuntu3) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

# dpkg -l akonadi-backend-sqlite
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-======================-==================-============-==================================
ii akonadi-backend-sqlite 4:18.12.3-0ubuntu3 amd64 SQLite storage backend for Akonadi

# apt-get install akonadi-backend-mysql
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  akonadi-server libmecab2 mysql-community-client-core mysql-community-server-core
Suggested packages:
  akonadi-backend-postgresql
Recommended packages:
  mecab-ipadic-utf8
The following NEW packages will be installed:
  akonadi-backend-mysql akonadi-server libmecab2 mysql-community-client-core mysql-community-server-core
0 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
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