Fallback to psutil when /proc/.../children isn't present

[Kamori]

I'm developing a project using Ubuntu 18.04 on Windows WSL2. For some reason /proc/{pid}/task/{pid}/children isn't available. When this happened, we return with no good explanation why.

To make sure we don't break current users, I added a fallback to psutil to discover the children and kill them and move on.

Hope this helps others who use WSL2

Edit: This affects the live reloading feature

[Tronic]

The code patched here is removed entirely in #1827 which rewrites the autoreloader kill logic (i.e. the autoreloader signals the main server, which then signals its children, avoiding the need to kill all children).

@Kamori Would you mind testing that PR to see if it also works for you?

[ahopkins]

@Kamori Thanks for the PR. I am placing on hold until we see if this is still necessary once #1827 is merged.

[Kamori]

Sorry for the delay. I'll test this when I can. Hopefully tomorrow

[Kamori]

First test seems to work well! I'm gonna do a bit of development today to make sure I don't run into any issues. I'll close this ticket out if all looks good. Thanks everyone!