The output you have put here states everything you need to solve this issue, including a link to a further explanation. It is not a bug, let alone a blocker, and you should close this issue; it should have been a post to the mailing list at most.
There are two logging implementation jars on your classpath. In this scenario which binding class is used at runtime is undefined; as it happens, the one in slf4j-nop-1.7.5.jar is being chosen on centos 7 and the one in logback-classic-1.0.0.jar is being chosen on centos 6. You have code that assumes the implementation is logback classic, which consequently fails when it is not.
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
The output you have put here states everything you need to solve this issue, including a link to a further explanation. It is not a bug, let alone a blocker, and you should close this issue; it should have been a post to the mailing list at most.
There are two logging implementation jars on your classpath. In this scenario which binding class is used at runtime is undefined; as it happens, the one in slf4j-nop-1.7.5.jar is being chosen on centos 7 and the one in logback-classic-1.0.0.jar is being chosen on centos 6. You have code that assumes the implementation is logback classic, which consequently fails when it is not.