Provide better error handling, when emulator falls

[MaxStalker]

One easy way to mess up your emulator is to provide non-existing contract for deployment (for example, adding .cdc extension at the end)

In your flow.json:

        "deployments": {
		"emulator": {
			"emulator-account": [
				"MyFancyContract.cdc`
			]
		}
	}

Emulator will exit with error deployment contains nonexisting contract MyFancyContract.cdc.
But tests will fail with Error: Response closed without headers - which gives nothing to work with.