improve formatting of error messages

src/wormhole/cli/runner.py

@@ -1,10 +1,10 @@
 from __future__ import print_function
 import time
 start = time.time()
-import os, sys
+import os, sys, textwrap
 from twisted.internet.defer import maybeDeferred
 from twisted.internet.task import react
-from ..errors import TransferError, WrongPasswordError, Timeout
+from ..errors import TransferError, WrongPasswordError, WelcomeError, Timeout
 from ..timing import DebugTiming
 from .cli_args import parser
 top_import_finish = time.time()
@@ -48,9 +48,18 @@ def run(reactor, argv, cwd, stdout, stderr, executable=None):
         return res
     d.addBoth(_maybe_dump_timing)
     def _explain_error(f):
-        # these three errors don't print a traceback, just an explanation
-        f.trap(TransferError, WrongPasswordError, Timeout)
-        print("ERROR:", f.value, file=stderr)
+        # these errors don't print a traceback, just an explanation
+        f.trap(TransferError, WrongPasswordError, WelcomeError, Timeout)
+        if f.check(WrongPasswordError):
+            msg = textwrap.fill("ERROR: " + textwrap.dedent(f.value.__doc__))
+            print(msg, file=stderr)
+        elif f.check(WelcomeError):
+            msg = textwrap.fill("ERROR: " + textwrap.dedent(f.value.__doc__))
+            print(msg, file=stderr)
+            print(file=stderr)
+            print(str(f.value), file=stderr)
+        else:
+            print("ERROR:", f.value, file=stderr)
         raise SystemExit(1)
     d.addErrback(_explain_error)
     d.addCallback(lambda _: 0)

src/wormhole/errors.py

@@ -1,4 +1,4 @@
-import functools, textwrap
+import functools
 
 class ServerError(Exception):
     def __init__(self, message, relay):
@@ -21,8 +21,10 @@ class Timeout(Exception):
     pass
 
 class WelcomeError(Exception):
-    """The server told us to signal an error, probably because our version is
-    too old to possibly work."""
+    """
+    The relay server told us to signal an error, probably because our version
+    is too old to possibly work. The server said:"""
+    pass
 
 class WrongPasswordError(Exception):
     """
@@ -32,8 +34,7 @@ class WrongPasswordError(Exception):
     chance.
     """
     # or the data blob was corrupted, and that's why decrypt failed
-    def __init__(self):
-        Exception.__init__(self, textwrap.dedent(self.__doc__.strip()))
+    pass
 
 class ReflectionAttack(Exception):
     """An attacker (or bug) reflected our outgoing message back to us."""