[5.8.4] Running tapestry-spock based test

Testing the brand-new 5.8.4 release candidate, a

java.lang.NoClassDefFoundError: 
org/apache/tapestry5/plastic/internal/asm/ClassVisitor

occurs when running a tapestry-spock based test. The same test runs fine 
in 5.8.3.

The problem needs further analysis. Not sure if tapestry-spock is 
missing a dependency or if a transitive dependency is missing elsewhere. 
Will look at this further when I have more time. For now I wanted to 
share the observation in case someone else is experiencing similar issues.