Non deterministic tests

[jxson]

I noticed that I get an occasional test failure where stderr doesn't seem to be captured:

$ go test -v github.com/monopole/mdrip
=== RUN TestLex
--- PASS: TestLex (0.00s)
=== RUN TestRunnerWithNothing
All done, no errors triggered.
--- PASS: TestRunnerWithNothing (0.00s)
=== RUN TestRunnerWithGoodStuff
Running foo (1/3) from iAmFileName
Running foo (2/3) from iAmFileName
Running foo (3/3) from iAmFileName
All done, no errors triggered.
--- PASS: TestRunnerWithGoodStuff (0.01s)
=== RUN TestWithBadStuff1
Running foo (1/1) from iAmFileName
--- PASS: TestWithBadStuff1 (0.00s)
=== RUN TestWithBadStuff2
Running foo (1/4) from iAmFileName
Running foo (2/4) from iAmFileName
Running foo (3/4) from iAmFileName
--- FAIL: TestWithBadStuff2 (0.01s)
        runner_test.go:34: message got

            want
                bash: line 9: lochNessMonster: command not found
FAIL
exit status 1
FAIL    github.com/monopole/mdrip   0.040s

[jxson]

It seems to always fail on travis: https://travis-ci.org/jxson/mdrip/builds/64316805