It's possible to create collection names like "test.index_bounds_pipe/^a|b/". During rollback we try to write a rollback file for this but get the following error: FileNotOpen: couldn't create file: /data/db/job6/resmoke/node0/rollback/test.index_bounds_pipe/^a|b/.2018-06-20T16-00-53.0.bson for remove saving: No such file or directory. We should change these names to ones the file system recognizes and ensure that collisions are handled properly.