Ceph

The following packages have unmet dependencies:
 ceph-libboost-regex1.67-dev : Depends: ceph-libboost-regex1.67.0 (= 1.67.0-7) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

If you try to install 'ceph-libboost-regex1.67.0' you get...

# apt-get install ceph-libboost-regex1.67.0
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:
 ceph-libboost-regex1.67.0 : Depends: libicu55 (>= 55.1-1~) but it is not installable
E: Unable to correct problems, you have held broken packages.

libicu55 does not appear to be available in Bionic and appears to have been replaced by libicu60.

looks like we need to remove the dependency of 'ceph-libboost-regex1.67-dev' on 'ceph-libboost-regex1.67.0' or the dependency of 'ceph-libboost-regex1.67.0' on libicu55.