The mozprofile 0.2 crate on crates.io contains an Emacs backup file, src/prefdata.rs~. This causes problems when importing geckodriver to mozilla-central (https://bugzilla.mozilla.org/show_bug.cgi?id=1340637) because it has .gitignore/.hgignore files that don’t let you add this file.
This again causes problems when the patches to build geckodriver in m-c run on the build slaves because cargo fails the integrity check of the crate package, as can be seen in https://treeherder.mozilla.org/logviewer.html#?job_id=78421179&repo=try&lineNumber=5064.