Reformat evaluator #1

smnp/error/base.py

@@ -1,2 +1,13 @@
 class SmnpException(Exception):
-    pass
+    def __init__(self, msg, pos):
+        self.msg = msg
+        self.pos = pos
+
+    def _title(self):
+        pass
+
+    def _position(self):
+        return "" if self.pos is None else f" [line {self.pos[0]+1}, col {self.pos[1]+1}]"
+
+    def message(self):
+        return f"{self._title()}{self._position()}:\n{self.msg}"