To report a bug, open an issue at GitHub. You can also email us, but GitHub issues are preferred because we won't forget about them.

If you write code to fix a bug, reference the issue number in the commit message. This makes it a lot easier to look back at old issues and figure out how they were resolved. (If the code you write does not fix the bug but only relates to it, for example if you write a test case that demonstrates the problem, then you should also link it to the issue, using "relates" rather than "closes" in your commit message.)