30271
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11160 add #classBuilder to nil
https://pharo.fogbugz.com/f/cases/11160
11153 Introduce Exception >> #signalIn:
https://pharo.fogbugz.com/f/cases/11153
Diff information:
http://smalltalkhub.com/mc/Pharo/Pharo30/main/KernelTests-MarcusDenker.529.diff
http://smalltalkhub.com/mc/Pharo/Pharo30/main/Kernel-MarcusDenker.1520.diff
