Merge pull request psychopy#7494 from wadelab/fix-keyboard-buffers-attribute-error

Fix AttributeError: KeyboardDevice missing _buffers attribute wo PTB

Author: peircej

psychopy/hardware/keyboard.py

@@ -386,6 +386,12 @@ def __init__(self, device=-1, bufferSize=10000, waitForStart=False, clock=None,
 
         logging.info('keyboard.Keyboard is using %s backend.' % KeyboardDevice._backend)
 
+        # Initialize _buffers and _devs for all backends to prevent AttributeError
+        if not hasattr(self, '_buffers'):
+            self._buffers = {}
+        if not hasattr(self, '_devs'):
+            self._devs = {}
+
         # array in which to store ongoing presses
         self._keysStillDown = deque()
         # set whether or not to mute any keypresses which happen outside of PsychoPy