add InvalidIsotopeError and DimensionError

src/pg_rad/exceptions/exceptions.py

@@ -14,12 +14,20 @@ class OutOfBoundsError(Exception):
     """Raised when an object is attempted to be placed out of bounds."""
 
 
-class MissingNestedKeyError(Exception):
-    """Raised when a nested key is missing in the config."""
+class MissingConfigKeyError(KeyError):
+    """Raised when a (nested) config key is missing in the config."""
     def __init__(self, key, subkey=None):
         if subkey:
-            self.message = f"Missing key in {key}: {subkey}"
+            self.message = f"Missing key in {key}: {', '.join(list(subkey))}"
         else:
             self.message = f"Missing key: {key}"
 
         super().__init__(self.message)
+
+
+class DimensionError(ValueError):
+    """Raised if dimensions or coordinates do not match the system."""
+
+
+class InvalidIsotopeError(ValueError):
+    """Raised if attempting to load an isotope that is not valid."""