v2: investigate odd JSONEncoding exceptions when using orders cli against server

[jreiberkyle]

In testing live testing of #284, some weird bugs have popped up that require further investigation.

1. planet orders list —limit 40 succeeds while planet orders list or planet orders list —limit 45 fail with a JSONEncoding exception. Is there something going on at the end of the pages, like an empty page? Or is there a wacky order? Its a mystery!

2. Trying to download an order after trying to cancel it, results in a JSONEncoding exception.

$ export OID=$(planet orders list --limit 1 | jq '.[0]["id"]' -r)
$ planet orders download $OID

This is fine

But if we do cancel (which supposedly fails because the order isn't in a cancelable state), and then try to download without much delay, we get a JSONException

$ planet orders cancel $OID
$ planet orders download $OID

Wait a bit before trying to download, and we get no exception.

[jreiberkyle]

This bug is caused by an error in parsing the response when certain API exceptions are raised. It is both introduced and resolved in #284.