add gpio mocks for testing

screenless/bureau/photography/photography.py

@@ -1,7 +1,15 @@
 import subprocess
 import tempfile
 
+try:
     from pyA20.gpio import gpio, port
+except ImportError:
+    from unittest.mock import Mock
+    gpio = Mock()
+    class Tmpobj():
+        pass
+    port = Tmpobj()
+    port.PG0 = 42
 
 from bureau import Bureau, add_api