snap: Start snap support.

- Create a snapcraft.yaml file in snap directory.
  Couldn't put this in packaging directory.
- Use make-snapcraft.py to generate the snapcraft file.
- Use make-snap to make the snap from the snapcraft file.
- Eris is confined to only access projects in home.
- os.setpriority doesn't work in snaps.
- eris-webserver is run as "eris.webserver".

eris/eris/tools.toml

@@ -148,7 +148,7 @@ tools_for_extensions = [
 [unrar]
   dependencies = ["unrar"]
   url = "http://www.rarlabs.com/"
-  command = "unrar l"
+  command = "unrar-nonfree l"
 
 [7z]
   dependencies = ["p7zip"]
@@ -214,7 +214,7 @@ tools_for_extensions = [
   has_color = true
 
 [php8_syntax]
-  dependencies = ["php8.0-cli"]
+  dependencies = ["php-cli"]
   url = "https://en.wikipedia.org/wiki/PHP"
   command = "php --syntax-check"
 
@@ -237,7 +237,7 @@ tools_for_extensions = [
 [lua_syntax]
   dependencies = ["lua5.3"]
   url = "http://www.lua.org"
-  command = "luac -p"
+  command = "luac5.3 -p"
 
 [js_syntax]
   dependencies = ["nodejs"]

eris/eris/worker.py

@@ -31,7 +31,8 @@ class Worker:
         self.process = await create
         pid_line = await self.process.stdout.readline()
         self.child_pgid = int(pid_line.strip())
-        os.setpriority(os.PRIO_PGRP, self.child_pgid, 19)
+        if "SNAP" not in os.environ:  # Can't do setpriority inside snaps.
+            os.setpriority(os.PRIO_PGRP, self.child_pgid, 19)
         self.process.stdin.write(f"{self.compression}\n".encode("utf-8"))
 
     async def run_tool(self, path, tool):