Fix creating containers with env vars with unicode characters

Signed-off-by: Fernando Mayo <fernando@docker.com>

docker/utils/utils.py

@@ -993,7 +993,7 @@ def format_environment(environment):
     def format_env(key, value):
         if value is None:
             return key
-        return '{key}={value}'.format(key=key, value=value)
+        return u'{key}={value}'.format(key=key, value=value)
     return [format_env(*var) for var in six.iteritems(environment)]
 
 

tests/unit/container_test.py

+# -*- coding: utf-8 -*-
+
 import datetime
 import json
 import signal
@@ -1155,6 +1157,24 @@ class CreateContainerTest(DockerClientTest):
             args[1]['timeout'], DEFAULT_TIMEOUT_SECONDS
         )
 
+    def test_create_container_with_unicode_envvars(self):
+        envvars_dict = {
+            'foo': u'☃',
+        }
+
+        expected = [
+            u'foo=☃'
+        ]
+
+        self.client.create_container(
+            'busybox', 'true',
+            environment=envvars_dict,
+        )
+
+        args = fake_request.call_args
+        self.assertEqual(args[0][1], url_prefix + 'containers/create')
+        self.assertEqual(json.loads(args[1]['data'])['Env'], expected)
+
 
 class ContainerTest(DockerClientTest):
     def test_list_containers(self):