Coding style.

Using asyncio coroutines for workers instead of threads.

worker.py

@@ -4,50 +4,10 @@
 # Licensed under the Artistic License 2.0.
 
 import os
-import signal
-import subprocess
-
-import psutil
 
 import tools
 
 
-def _make_process_nicest(pid):
-    process = psutil.Process(pid)
-    process.nice(19)
-    process.ionice(psutil.IOPRIO_CLASS_IDLE)
-
-
-class Worker:
-
-    def __init__(self, sandbox):
-        self.sandbox = sandbox
-        if sandbox is None:
-            self.process = subprocess.Popen(
-                [__file__], stdin=subprocess.PIPE, stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE)
-        else:
-            cache_path = os.path.join(os.getcwd(), tools.CACHE_PATH)
-            self.cache_mount = sandbox.mount_point + cache_path
-            subprocess.check_call(["sudo", "mount", "--bind", cache_path,
-                                   self.cache_mount])
-            self.process = sandbox.Popen([__file__])
-        self.child_pid = int(self.process.stdout.readline())
-        _make_process_nicest(self.child_pid)
-
-    def run_tool(self, path, tool):
-        self.process.stdin.write(("%s\n%s\n" %
-                                  (tool.__qualname__, path)).encode("utf-8"))
-        self.process.stdin.flush()
-        return tools.Status(int(self.process.stdout.readline()))
-
-    def pause(self):
-        os.kill(self.child_pid, signal.SIGSTOP)
-
-    def continue_(self):
-        os.kill(self.child_pid, signal.SIGCONT)
-
-
 def main():
     print(os.getpid(), flush=True)
     while True: