adopt myst

run rst2myst, with minimal manual formatting fixes

docs/troubleshooting/providers/custom.md

@@ -0,0 +1,30 @@
+(troubleshooting-providers-custom)=
+
+# Troubleshooting issues on your own server
+
+This is an incomplete list of issues people have run into
+when installing TLJH on their own servers, and ways they
+have fixed them.
+Before trying any of them, also consider whether turning your machine on and off
+and/or deleting the VM and starting over could solve the problem;
+it has done so on a surprisingly high number of occasions!
+
+## Outgoing HTTP proxy required
+
+If your server is behind a firewall that requires a HTTP proxy to reach
+the internet, run these commands before running the installer
+
+```bash
+export http_proxy=<your_proxy-server>
+```
+
+## HTTPS certificate interception
+
+If your server is behind a firewall that intercepts HTTPS requests
+and re-signs them, you might have to explicitly tell TLJH which
+certificates to use.
+
+```
+export REQUESTS_CA_BUNDLE=</directory/with/your/ssl/certificates>
+sudo npm config set cafile=</directory/with/your/ssl/certificates>
+```