OSVM `201804030952` sometimes crashes in `Context(Object)>copy` when running Squeak SUnit tests.
Full stack trace at: https://travis-ci.org/squeak-smalltalk/squeak-app/jobs/387262157#L2073
Another trace is at: https://travis-ci.org/squeak-smalltalk/squeak-app/jobs/382950107#L1717