diff --git a/src/allmydata/scripts/tahoe_add_alias.py b/src/allmydata/scripts/tahoe_add_alias.py
index 1252b0e72..51d48e5a3 100644
--- a/src/allmydata/scripts/tahoe_add_alias.py
+++ b/src/allmydata/scripts/tahoe_add_alias.py
@@ -98,6 +98,20 @@ def create_alias(options):
 
 
 def show_output(fp, template, **kwargs):
+    """
+    Print to just about anything.
+
+    :param fp: A file-like object to which to print.  This handles the case
+        where ``fp`` declares a support encoding with the ``encoding``
+        attribute (eg sys.stdout on Python 3).  It handles the case where
+        ``fp`` declares no supported encoding via ``None`` for its
+        ``encoding`` attribute (eg sys.stdout on Python 2 when stdout is not a
+        tty).  It handles the case where ``fp`` declares an encoding that does
+        not support all of the characters in the output by forcing the
+        "namereplace" error handler.  It handles the case where there is no
+        ``encoding`` attribute at all (eg StringIO.StringIO) by writing
+        utf-8-encoded bytes.
+    """
     assert isinstance(template, unicode)
 
     # On Python 3 fp has an encoding attribute under all real usage.  On
@@ -105,13 +119,22 @@ def show_output(fp, template, **kwargs):
     # test suite often passes StringIO which has no such attribute.  Make
     # allowances for this until the test suite is fixed and Python 2 is no
     # more.
-    encoding = getattr(fp, "encoding", None) or "utf-8"
+    try:
+        encoding = fp.encoding or "utf-8"
+    except AttributeError:
+        has_encoding = False
+        encoding = "utf-8"
+    else:
+        has_encoding = True
+
     output = template.format(**{
         k: quote_output_u(v, encoding=encoding)
         for (k, v)
         in kwargs.items()
     })
-    safe_output = output.encode(encoding, "namereplace").decode(encoding)
+    safe_output = output.encode(encoding, "namereplace")
+    if has_encoding:
+        safe_output = safe_output.decode(encoding)
     print(safe_output, file=fp)
 
 
diff --git a/src/allmydata/test/cli/common.py b/src/allmydata/test/cli/common.py
index e4c96bab8..3da959604 100644
--- a/src/allmydata/test/cli/common.py
+++ b/src/allmydata/test/cli/common.py
@@ -1,6 +1,6 @@
 from ...util.encodingutil import unicode_to_argv
 from ...scripts import runner
-from ..common_util import ReallyEqualMixin, run_cli, run_cli_ex
+from ..common_util import ReallyEqualMixin, run_cli, run_cli_unicode
 
 def parse_options(basedir, command, args):
     o = runner.Options()
@@ -10,12 +10,12 @@ def parse_options(basedir, command, args):
     return o
 
 class CLITestMixin(ReallyEqualMixin):
-    def do_cli_ex(self, verb, argv, client_num=0, **kwargs):
+    def do_cli_unicode(self, verb, argv, client_num=0, **kwargs):
         # client_num is used to execute client CLI commands on a specific
         # client.
         client_dir = self.get_clientdir(i=client_num)
         nodeargs = [ u"--node-directory", client_dir ]
-        return run_cli_ex(verb, argv, nodeargs=nodeargs, **kwargs)
+        return run_cli_unicode(verb, argv, nodeargs=nodeargs, **kwargs)
 
 
     def do_cli(self, verb, *args, **kwargs):
diff --git a/src/allmydata/test/cli/test_alias.py b/src/allmydata/test/cli/test_alias.py
index 9064a8c2b..9a2b35c8c 100644
--- a/src/allmydata/test/cli/test_alias.py
+++ b/src/allmydata/test/cli/test_alias.py
@@ -17,22 +17,24 @@ class ListAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
         self.basedir = self.mktemp()
         self.set_up_grid(oneshare=True)
 
-        rc, stdout, stderr = yield self.do_cli_ex(
+        rc, stdout, stderr = yield self.do_cli_unicode(
             u"create-alias",
             [alias],
             encoding=encoding,
         )
 
-        self.assertIn(
-            b"Alias {} created".format(quote_output(alias, encoding=encoding)),
-            stdout.encode(encoding),
+        self.assertEqual(
+            b"Alias {} created\n".format(
+                quote_output(alias, encoding=encoding),
+            ),
+            stdout,
         )
         self.assertEqual("", stderr)
         aliases = get_aliases(self.get_clientdir())
         self.assertIn(alias, aliases)
         self.assertTrue(aliases[alias].startswith(u"URI:DIR2:"))
 
-        rc, stdout, stderr = yield self.do_cli_ex(
+        rc, stdout, stderr = yield self.do_cli_unicode(
             u"list-aliases",
             [u"--json"],
             encoding=encoding,
@@ -60,3 +62,11 @@ class ListAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_list_nonascii_utf_8(self):
         return self._test_list(u"tahoe\N{SNOWMAN}", encoding="utf-8")
+
+
+    def test_list_none(self):
+        return self._test_list(u"tahoe", encoding=None)
+
+
+    def test_list_nonascii_none(self):
+        return self._test_list(u"tahoe\N{SNOWMAN}", encoding=None)
diff --git a/src/allmydata/test/cli/test_create_alias.py b/src/allmydata/test/cli/test_create_alias.py
index 324b2364a..ea3200e2e 100644
--- a/src/allmydata/test/cli/test_create_alias.py
+++ b/src/allmydata/test/cli/test_create_alias.py
@@ -6,7 +6,7 @@ from allmydata.util import fileutil
 from allmydata.scripts.common import get_aliases
 from allmydata.scripts import cli, runner
 from ..no_network import GridTestMixin
-from allmydata.util.encodingutil import quote_output_u, get_io_encoding
+from allmydata.util.encodingutil import quote_output, get_io_encoding
 from .common import CLITestMixin
 
 class CreateAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
@@ -171,15 +171,7 @@ class CreateAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
             (rc, out, err) = args
             self.failUnlessReallyEqual(rc, 0)
             self.failUnlessReallyEqual(err, "")
-            self.assertIn(
-                u"Alias %s created" % (
-                    quote_output_u(
-                        u"\u00E9tudes",
-                        encoding=get_io_encoding(),
-                    ),
-                ),
-                out.decode(get_io_encoding()),
-            )
+            self.failUnlessIn("Alias %s created" % quote_output(u"\u00E9tudes"), out)
 
             aliases = get_aliases(self.get_clientdir())
             self.failUnless(aliases[u"\u00E9tudes"].startswith("URI:DIR2:"))
diff --git a/src/allmydata/test/common_util.py b/src/allmydata/test/common_util.py
index 48e89a851..8b4a33197 100644
--- a/src/allmydata/test/common_util.py
+++ b/src/allmydata/test/common_util.py
@@ -48,55 +48,18 @@ def _getvalue(io):
     return io.read()
 
 
-def run_cli(verb, *args, **kwargs):
-    """
-    Run some CLI command using Python 2 stdout/stderr semantics.
-    """
+def run_cli_bytes(verb, *args, **kwargs):
     nodeargs = kwargs.pop("nodeargs", [])
-    stdin = kwargs.pop("stdin", None)
+    encoding = kwargs.pop("encoding", None)
     precondition(
-        all(isinstance(arg, bytes) for arg in [verb] + (nodeargs or []) + list(args)),
+        all(isinstance(arg, bytes) for arg in [verb] + nodeargs + list(args)),
         "arguments to run_cli must be bytes -- convert using unicode_to_argv",
         verb=verb,
         args=args,
         nodeargs=nodeargs,
     )
-    encoding = "utf-8"
-    d = run_cli_ex(
-        verb=verb.decode(encoding),
-        argv=list(arg.decode(encoding) for arg in args),
-        nodeargs=list(nodearg.decode(encoding) for nodearg in nodeargs),
-        stdin=stdin,
-    )
-    def maybe_encode(result):
-        code, stdout, stderr = result
-        # Make sure we produce bytes output since that's what all the code
-        # written to use this interface expects.  If you don't like that, use
-        # run_cli_ex instead.  We use get_io_encoding here to make sure that
-        # whatever was written can actually be encoded that way, otherwise it
-        # wouldn't really be writeable under real usage.
-        if isinstance(stdout, unicode):
-            stdout = stdout.encode(encoding)
-        if isinstance(stderr, unicode):
-            stderr = stderr.encode(encoding)
-        return code, stdout, stderr
-    d.addCallback(maybe_encode)
-    return d
-
-
-def run_cli_ex(verb, argv, nodeargs=None, stdin=None, encoding=None):
-    precondition(
-        all(isinstance(arg, unicode) for arg in [verb] + (nodeargs or []) + argv),
-        "arguments to run_cli_ex must be unicode",
-        verb=verb,
-        nodeargs=nodeargs,
-        argv=argv,
-    )
-    if nodeargs is None:
-        nodeargs = []
-    argv = nodeargs + [verb] + list(argv)
-    if stdin is None:
-        stdin = ""
+    argv = nodeargs + [verb] + list(args)
+    stdin = kwargs.get("stdin", "")
     if encoding is None:
         # The original behavior, the Python 2 behavior, is to accept either
         # bytes or unicode and try to automatically encode or decode as
@@ -126,6 +89,38 @@ def run_cli_ex(verb, argv, nodeargs=None, stdin=None, encoding=None):
     d.addCallbacks(_done, _err)
     return d
 
+
+def run_cli_unicode(verb, argv, nodeargs=None, stdin=None, encoding=None):
+    if nodeargs is None:
+        nodeargs = []
+    precondition(
+        all(isinstance(arg, unicode) for arg in [verb] + nodeargs + argv),
+        "arguments to run_cli_unicode must be unicode",
+        verb=verb,
+        nodeargs=nodeargs,
+        argv=argv,
+    )
+    d = run_cli_bytes(
+        verb.encode("utf-8"),
+        nodeargs=list(arg.encode("utf-8") for arg in nodeargs),
+        stdin=stdin,
+        encoding=encoding,
+        *list(arg.encode("utf-8") for arg in argv)
+    )
+    def maybe_decode(result):
+        code, stdout, stderr = result
+        if isinstance(stdout, unicode):
+            stdout = stdout.encode("utf-8")
+        if isinstance(stderr, unicode):
+            stderr = stderr.encode("utf-8")
+        return code, stdout, stderr
+    d.addCallback(maybe_decode)
+    return d
+
+
+run_cli = run_cli_bytes
+
+
 def parse_cli(*argv):
     # This parses the CLI options (synchronously), and returns the Options
     # argument, or throws usage.UsageError if something went wrong.