Fix patroni no longer working with update to ydiff 1.3

ydiff 1.3.0 was released on April 2, 2024
(https://pypi.org/project/ydiff/#history), and the patroni install
quietly updated to ydiff 1.3.0 from 1.2.0.

https://github.com/zalando/patroni/blob/v3.0.1/requirements.txt#L15
allows any version of ydiff above 1.2.0, but as described in
https://github.com/zalando/patroni/blob/634b44ee0586f063033074806a42b534a354cbff/docs/releases.rst#L16
ydiff 1.3 requires the cdiff module.

To fix this problem, pin the version of ydiff to 1.2.0 until
we can upgrade patroni.

Changelog: fixed

Author: stanhu

config/software/patroni.rb

@@ -35,5 +35,13 @@
   # https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/5701
   command "#{install_dir}/embedded/bin/pip3 install prettytable==0.7.2", env: env
 
+  # Pin ydiff to 1.2 since 1.3 requires cdiff:
+  # https://github.com/zalando/patroni/blob/634b44ee0586f063033074806a42b534a354cbff/docs/releases.rst
+  # According to Patroni 3.3.0 release notes, upgrading to this version
+  # should be enough to fix this problem. We should test unpinning
+  # this library once we update to Patroni 3.3.0.
+  # See: https://github.com/zalando/patroni/blob/634b44ee0586f063033074806a42b534a354cbff/docs/releases.rst
+  command "#{install_dir}/embedded/bin/pip3 install ydiff==1.2", env: env
+
   command "#{install_dir}/embedded/bin/pip3 install patroni[consul]==#{version}", env: env
 end