cli.test_alias: move skip-unless utility to common_util.py

next to the other skip-unless function

src/allmydata/test/cli/test_alias.py

@@ -4,22 +4,14 @@ from mock import patch
 from twisted.trial import unittest
 from twisted.internet.defer import inlineCallbacks
 
-from allmydata.util.encodingutil import unicode_to_argv, get_io_encoding
+from allmydata.util.encodingutil import unicode_to_argv
 from allmydata.scripts.common import get_aliases
 from allmydata.test.no_network import GridTestMixin
 from .common import CLITestMixin
-
+from ..common_util import skip_if_cannot_represent_argv
 
 # see also test_create_alias
 
-def skip_unless_unicode():
-    try:
-        etudes_arg = u"\u00E9tudes".encode(get_io_encoding())
-        del etudes_arg
-    except UnicodeEncodeError:
-        raise unittest.SkipTest("A non-ASCII command argument could not be encoded on this platform.")
-
-
 class ListAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     @inlineCallbacks
@@ -55,7 +47,7 @@ class ListAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
         this
         """
         self.basedir = "cli/ListAlias/test_list_unicode_mismatch_json"
-        skip_unless_unicode()
+        skip_if_cannot_represent_argv(u"tahoe\u263A")
         self.set_up_grid(oneshare=True)
 
         rc, stdout, stderr = yield self.do_cli(
@@ -87,7 +79,7 @@ class ListAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
     @inlineCallbacks
     def test_list_unicode_mismatch(self):
         self.basedir = "cli/ListAlias/test_list_unicode_mismatch"
-        skip_unless_unicode()
+        skip_if_cannot_represent_argv(u"tahoe\u263A")
         self.set_up_grid(oneshare=True)
 
         rc, stdout, stderr = yield self.do_cli(

src/allmydata/test/common_util.py

@@ -22,6 +22,13 @@ def skip_if_cannot_represent_filename(u):
         except UnicodeEncodeError:
             raise unittest.SkipTest("A non-ASCII filename could not be encoded on this platform.")
 
+def skip_if_cannot_represent_argv(u):
+    precondition(isinstance(u, unicode))
+    try:
+        u.encode(get_io_encoding())
+    except UnicodeEncodeError:
+        raise unittest.SkipTest("A non-ASCII argv could not be encoded on this platform.")
+
 def run_cli(verb, *args, **kwargs):
     precondition(not [True for arg in args if not isinstance(arg, str)],
                  "arguments to do_cli must be strs -- convert using unicode_to_argv", args=args)