check if pins exist before using

Author: FoamyGuy

tests/circuitpython-manual/usb/device_info.py

@@ -9,7 +9,8 @@
     d.switch_to_output(value=True)
     print("USB power on")
 
-h = usb_host.Port(board.USB_HOST_DP, board.USB_HOST_DM)
+if hasattr(board, "USB_HOST_DP") and hasattr(board, "USB_HOST_DM"):
+    h = usb_host.Port(board.USB_HOST_DP, board.USB_HOST_DM)
 
 while True:
     for device in usb.core.find(find_all=True):