Move autograde_wrapper guts into a main() function

This cleans up some warnings

autodriver/autograde_wrapper.py

@@ -20,46 +20,50 @@ def __call__(self):
             while np is None or np != self.waitfor:
                 (np, self.status)=os.wait()
         except OSError:
-            if pid:
+            if np:
                 print("Chld process {} never exited, but no more children left".format(self.waitfor))
                 self.status=-1
 
-for f in os.listdir("mount"):
-    src=os.path.join("mount", f)
-    dst=os.path.join("autolab", f)
-    shutil.copy(src, dst)
+def main():
+    for f in os.listdir("mount"):
+        src=os.path.join("mount", f)
+        dst=os.path.join("autolab", f)
+        shutil.copy(src, dst)
 
-autolabuser=pwd.getpwnam("autolab")
-(r_p, w_p)=os.pipe()
-pid=os.fork()
-if pid == 0:
-    os.close(r_p)
-    os.setgroups([])
-    os.setgid(autolabuser.pw_gid)
-    os.setuid(autolabuser.pw_uid)
-    args=["autodriver"]
-    args.extend(sys.argv[1:])
-    args.append("autolab")
-    if w_p != 1:
-        os.dup2(w_p, 1)
-    if w_p != 2:
-        os.dup2(w_p, 2)
-    if w_p > 2:
-        os.close(w_p)
-    os.execvp(args[0], args)
-os.close(w_p)
-waiter=WaitLoop(pid)
-thr=threading.Thread(target=waiter)
-thr.start()
-rpf=os.fdopen(r_p)
-shutil.copyfileobj(rpf, open("mount/feedback", "w"))
-#print("Copied output")
-rpf.close()
-thr.join()
-# if core, exit -1, else pass through code.
-if os.WIFSIGNALED(waiter.status):
-    status=-1
-else:
-    status=os.WEXITSTATUS(waiter.status)
-#print("Status is {}".format(status))
-sys.exit(status)
+    autolabuser=pwd.getpwnam("autolab")
+    (r_p, w_p)=os.pipe()
+    pid=os.fork()
+    if pid == 0:
+        os.close(r_p)
+        os.setgroups([])
+        os.setgid(autolabuser.pw_gid)
+        os.setuid(autolabuser.pw_uid)
+        args=["autodriver"]
+        args.extend(sys.argv[1:])
+        args.append("autolab")
+        if w_p != 1:
+            os.dup2(w_p, 1)
+        if w_p != 2:
+            os.dup2(w_p, 2)
+        if w_p > 2:
+            os.close(w_p)
+        os.execvp(args[0], args)
+    os.close(w_p)
+    waiter=WaitLoop(pid)
+    thr=threading.Thread(target=waiter)
+    thr.start()
+    rpf=os.fdopen(r_p)
+    shutil.copyfileobj(rpf, open("mount/feedback", "w"))
+    #print("Copied output")
+    rpf.close()
+    thr.join()
+    # if core, exit -1, else pass through code.
+    if os.WIFSIGNALED(waiter.status):
+        status=-1
+    else:
+        status=os.WEXITSTATUS(waiter.status)
+    #print("Status is {}".format(status))
+    sys.exit(status)
+
+if __name__ == '__main__':
+    main()