Added stage tests and tidied up rescue

openflexure_microscope/rescue/check_picamera.py

@@ -1,5 +1,10 @@
 import logging
 
+from .error_sources import ErrorSource, WarningSource
+
+picamera_import_error = ErrorSource(
+    "Picamera module could not be imported. Check physical connections to the camera as it may be damaged."
+)
 
 def main():
     error_sources = []
@@ -11,6 +16,6 @@ def main():
         # TODO: Parse exception object for a few different issues, and append different error sources
         # E.g. pi with camera already in use, disconnected, unsupported OS, etc
         logging.error(e)
-        error_sources.append("picamera_import_error")
+        error_sources.append(picamera_import_error)
 
     return error_sources