id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,pull_request,body,repo,type,active_lock_reason,performed_via_github_app,reactions,draft,state_reason
638241779,MDU6SXNzdWU2MzgyNDE3Nzk=,846,"""Too many open files"" error running tests",9599,closed,0,,,6,2020-06-13T22:11:40Z,2020-06-14T00:26:31Z,2020-06-14T00:26:31Z,OWNER,,"I got this on my laptop:
```pytest
...
/Users/simon/.local/share/virtualenvs/datasette-AWNrQs95/lib/python3.7/site-packages/jinja2/loaders.py:171: in get_source
    f = open_if_exists(filename)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

filename = '/Users/simon/Dropbox/Development/datasette/datasette/templates/400.html', mode = 'rb'

    def open_if_exists(filename, mode='rb'):
        """"""Returns a file descriptor for the filename if that file exists,
        otherwise `None`.
        """"""
        try:
>           return open(filename, mode)
E           OSError: [Errno 24] Too many open files: '/Users/simon/Dropbox/Development/datasette/datasette/templates/400.html'

/Users/simon/.local/share/virtualenvs/datasette-AWNrQs95/lib/python3.7/site-packages/jinja2/utils.py:154: OSError
```
Based on the conversation in https://github.com/pytest-dev/pytest/issues/2970 I'm worried that my tests are opening too many files without closing them.

In particular... I call `sqlite3.connect(filepath)` a LOT - and I don't ever call `conn.close()` on those opened connections:

https://github.com/simonw/datasette/blob/cf7a2bdb404734910ec07abc7571351a2d934828/datasette/database.py#L58-L60

Could this be resulting in my tests eventually opening too many unclosed file handles? How could I confirm this?",107914493,issue,,,"{""url"": ""https://api.github.com/repos/simonw/datasette/issues/846/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed