end-to-end not exiting on fatal Rust executor errors

[echeran]

The Rust executor is getting an error when trying to execute sendOneLine, and it does so for every batch of 10,000 tests that it sends.

Ex:

Testing ../executors/rust/target/release/executor / coll_shift_short. 190,000 of 192,707
Testing ../executors/rust/target/release/executor / coll_shift_short. 191,000 of 192,707
Testing ../executors/rust/target/release/executor / coll_shift_short. 192,000 of 192,707
!!! sendOneLine fails: input => {"label": "0190000", "string1": "\u2eb6!", "string2": "\u2eb6?", "test_type": "coll_shift_short"}
{"label": "0190001", "string1": "\u2eb6?", "string2": "\u2eb7!", "test_type": "coll_shift_short"}
...
#EXIT<. Err = [Errno 2] No such file or directory: '../executors/rust/target/release/executor'
!!!!!! processBatchOfTests: "platform error": "None"

Issues:

• The Python script running everything logs the entire batch of test cases upon this error. We shouldn't print those 10000 lines
• In cases where the Python script can't get the executors to do basic things properly, the Python script should exit with a non-zero exit code

Bonus points: in the future, we can use a logging library so that we can more easily control the behavior differently on our local machines vs. on CI