Added safe expression parsing and error handling #43

Job	Run time
deploy / Setup	7s
deploy / deploy-production-aws	0s
deploy / build-aws	0s
deploy / build-gcp (production) / Build GCP (production)	1m 39s
deploy / build-gcp (staging) / Build GCP (staging)	1m 52s
deploy / deploy-staging-aws	0s
deploy / deploy-gcp-staging / Deploy (staging)	28s
deploy / deploy-gcp-production / Deploy (production)	23s
	4m 29s

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