Sometimes the test suite hangs

[rgardner]

I first hit this on Travis when I was using set -e and set +e in the install script. I don't understand why removing those lines fixed the error cargo was returning though.

Now I'm hitting this when experiment with cov:

$ cargo +nightly cov clean && cargo +nightly cov test && cargo +nightly cov report --open
...
running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running debug/deps/integration_tests-40f703f134d886e1

running 7 tests
test test_exit_normal_large_negative ... test test_exit_normal_large_negative has been running for over 60 seconds
test test_command_not_found ... test test_command_not_found has been running for over 60 seconds
test test_simple_redirects ... test test_simple_redirects has been running for over 60 seconds
test test_stderr_redirect ... test test_stderr_redirect has been running for over 60 seconds
test test_simple_pipeline ... test test_simple_pipeline has been running for over 60 seconds
test test_simple_echo ... test test_simple_echo has been running for over 60 seconds
test test_syntax_error ... test test_syntax_error has been running for over 60 seconds

test test_simple_pipeline ... ok
test test_syntax_error ... ok
test test_simple_redirects ... ok
test test_command_not_found ... ok
test test_stderr_redirect ... ok
test test_simple_echo ... ok
test test_exit_normal_large_negative ... ok
...