Use .get instead of [] for strand classifcations (#391)

* .get instead of [] for strand classifcations

This gets around an uniformative KeyError raised when the run is not on.
The missing Keys are not logged (and should be), I have created a separate issue for that.

* Format for pre-commit

AAAAA

* Forgive me pre-commit for I have sinned

I should just do this in an IDE

* Edit default for missing classifications

src/readfish/read_until/base.py

@@ -201,9 +201,13 @@ def __init__(
             self.CacheType.__name__,
             filter_to,
         )
-
+        # When there is no run on, MinKNOW only returns a subset of read classifications, and our prefilter classes are not amongst them.
+        # This would then throw an uniformative KeyError. We now just carry on, and get to the point where we try to query about the run
+        # Which raises a more informative gRPC error instead.
+        # TODO - log the missing strands
         self.strand_classes = set(
-            self.lookup_read_class[x] for x in self.prefilter_classes
+            self.lookup_read_class.get(x, f"{x}_classification_unavailable")
+            for x in self.prefilter_classes
         )
 
         self.logger.debug("Strand-like classes are %s.", self.strand_classes)