Structural changes

src/pyrmv/errors/ps_errors.py

@@ -0,0 +1,13 @@
+class PsIncorrectParamError(Exception):
+    """
+    An invalid parameter combination was requested, i.e. the
+    defined range of stable segments encompassed all public
+    transport sections or it was attempted to search
+    forward/backward from the end/beginning of the
+    connection.
+    """
+    def __init__(self):
+        super().__init__(self.__doc__)
+
+    def __str__(self):
+        return self.__doc__