Raise a better exception if there's no PureData.

Author: QuLogic

nodebox/sound/process.py

@@ -228,6 +228,8 @@ def start(self):
         if self.patch is None \
         or not os.path.exists(self.patch):
             raise PDError, "no PD patch file at '%s'" % self.patch
+        if not self._path:
+            raise PDError, "no PD application found"
         if not os.path.exists(self._path):
             raise PDError, "no PD application at '%s'" % self._path
         if not self._process:
@@ -286,4 +288,4 @@ def data(self):
     def stop(self):
         self._socket.connections -= 1
         self._socket.close()
-        self._socket = None
+        self._socket = None