Merge pull request #160 from Shopify/rwstauner/codegen-compat #564

Job	Run time
test (ubuntu, head)	1m 31s
test (ubuntu, 3.3)	2m 38s
test (3.3, --enable-frozen-string-literal --debug-frozen-string-literal, ubuntu)	2m 20s
	6m 29s

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