Explanation of the fix:
mysql-devel seems to define some kind of "weak" reference to libressl-devel. The libopenssl-devel package does provide the same api so it can be used, too. But only if it is installed before or in one go.
Since puppet tries to install mysql-devel first and than libopenssl-devel, zypper detects an conflict and terminates.
The fix is to force puppet to install libopenssl-devel first.