Summary:
This is a quick patch for #955, pending investigation and fix.
Test Plan:
```shell
$ cd sharness/
$ ./test_load_example_github.t --long
ok 1 - should load sourcecred/example-github
ok 2 # skip should update the snapshot (missing UPDATE_SNAPSHOT of !CIRCLECI,LOADED_GITHUB,UPDATE_SNA
PSHOT)
ok 3 - should be identical to the snapshot
# passed all 3 test(s)
1..3
$ CIRCLECI=true ./test_load_example_github.t --long
ok 1 # skip should load sourcecred/example-github (missing !CIRCLECI of !CIRCLECI,EXPENSIVE,HAVE_GITH
UB_TOKEN)
ok 2 # skip should update the snapshot (missing UPDATE_SNAPSHOT,LOADED_GITHUB,!CIRCLECI of !CIRCLECI,
LOADED_GITHUB,UPDATE_SNAPSHOT)
ok 3 # skip should be identical to the snapshot (missing LOADED_GITHUB,!CIRCLECI of !CIRCLECI,LOADED_
GITHUB)
# passed all 3 test(s)
1..3
```
Ref.: <https://circleci.com/docs/2.0/env-vars/#built-in-environment-variables>
wchargin-branch: test-skip-failing-circleci
1e87fdaa07