Hi, I will let others discuss the feature itself, here are already some comments about your patch:

- In module_connect(), the ability to pass "factory" as a positional argument is broken, please restore the previous code; I'm afraid there is no better implementation, even if it's a copy of connection.__init__.
- I suggest to allow "uri" in all builds, and fail only when it's True on a non supported platform.
- In general, try to wrap C code in 80 columns (except for the ".. function::" directive in .rst files)
- IIRC a correct URI is file:///path/to/file but sqlite probably allows file:/path/to/file as well.
- The test function should use "from test.support import TESTFN" to get a temporary file name (but I agree that sqlite tests don't seem to follow Python standards)