libssh2 - sshd tests fail - help requested

Hello openssh maintainers,

I'm the maintainer for the package libssh2, and recently, a FTBFS bug 
was opened due to test_sshd tests fail [1].

In the build log, the tests test_sshd.test 1 and test_sshd.test 2.

The logs mentions a lot of messages like this:
"#  User sbuild not allowed because account is locked".

I didn't make any changes to the libssh2 package for a while and the 
package did built until january.

I'm wondering if a default configuration in openssh changed recently 
that could cause this ftbfs?

Thanks in advance for your help.

/Nicolas

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1129134