No source packages in APT repo?

[Shawn Heisey]

I added a deb-src entry to my APT config matching the deb entry:

deb https://repo.dovecot.org/ce-2.3-latest/ubuntu/focal focal main
deb-src https://repo.dovecot.org/ce-2.3-latest/ubuntu/focal focal main

When this is there, I see a warning when running "apt update".

W: Skipping acquire of configured file 'main/source/Sources' as 
repository 'https://repo.dovecot.org/ce-2.3-latest/ubuntu/focal focal 
InRelease' does not seem to provide it (sources.list entry misspelt?)

Were source packages excluded deliberately?  The github repo for dovecot 
does not have a "debian" directory, which is the other route that would 
allow me to build packages.

Thanks,
Shawn