fix tft-in-use-error

Author: brentru

adafruit_pyportal.py

@@ -167,11 +167,12 @@ def __init__(self, *, url=None, headers=None, json_path=None, regexp_path=None,
 
         self._debug = debug
 
-        if hasattr(board, 'TFT_BACKLIGHT'):
-            self._backlight = pulseio.PWMOut(board.TFT_BACKLIGHT)  # pylint: disable=no-member
-        elif hasattr(board, 'TFT_LITE'):
-            self._backlight = pulseio.PWMOut(board.TFT_LITE)  # pylint: disable=no-member
-        else:
+        try:
+            if hasattr(board, 'TFT_BACKLIGHT'):
+                self._backlight = pulseio.PWMOut(board.TFT_BACKLIGHT)  # pylint: disable=no-member
+            elif hasattr(board, 'TFT_LITE'):
+                self._backlight = pulseio.PWMOut(board.TFT_LITE)  # pylint: disable=no-member
+        except ValueError:
             self._backlight = None
         self.set_backlight(1.0)  # turn on backlight