BF: Print errors to stdoutFrame

Trackback error messages were starting on the StdOutFrame and finishing
on the console. Also, an error occured randomly causing psychopy to crash.
The crash would happen when printing whilst a traceback was printed.
With this fix, the crash has not reoccurred.

psychopy/app/builder/builder.py

@@ -124,7 +124,9 @@ def doCheck(self):
             # then check if the process ended
             # self.exit
         for line in self.proc.stderr.readlines():
-            sys.stdout.write(line)
+            self.queue.put(line)
+            if not line:
+                break
         return True
 
     def getBuffer(self):