feat[ux]: move exception hint to the end of the message (vyperlang#4154)

moved the `(hint: ...)` to be reported at the end of the exception to
improve the readability. the hint should be displayed after the actual
problem has been described, i.e. as the last item in the exception
message.

---------

Co-authored-by: Charles Cooper <[email protected]>

vyper/exceptions.py

@@ -97,10 +97,7 @@ def hint(self):
 
     @property
     def message(self):
-        msg = self._message
-        if self.hint:
-            msg += f"\n\n  (hint: {self.hint})"
-        return msg
+        return self._message
 
     def format_annotation(self, value):
         from vyper import ast as vy_ast
@@ -148,7 +145,16 @@ def format_annotation(self, value):
         node_msg = textwrap.indent(node_msg, "  ")
         return node_msg
 
+    def _add_hint(self, msg):
+        hint = self.hint
+        if hint is None:
+            return msg
+        return msg + f"\n  (hint: {self.hint})"
+
     def __str__(self):
+        return self._add_hint(self._str_helper())
+
+    def _str_helper(self):
         if not self.annotations:
             if self.lineno is not None and self.col_offset is not None:
                 return f"line {self.lineno}:{self.col_offset} {self.message}"