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The message

This was likely caused by:
 * Unofficial software packages not provided by Ubuntu Please use the tool 
'ppa-purge' from the ppa-purge package to remove software from a Launchpad PPA 
and try the upgrade again.

If none of this applies, then please report this bug using the command 
'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. ..

looks like it applies. A quick scan of your sources and I can see four
different releases for packages (12.04, 17.10, 18.04, 19.04) so you
should first remove the Unofficial software packages not provided by
Ubuntu (PPA's are 3rd party sources not provided by Ubuntu) then try

I've marked this as incomplete because unofficial sources are still
there. If you believe I am in error, please return this the status to
new and leave a comment as to why.

** Changed in: ubuntu-release-upgrader (Ubuntu)
       Status: New => Incomplete

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  impossible calculate upgrade of version

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