helper: replace email_as_* with email builtins

Python 3.3 added a new feature to the email module, policies
(https://docs.python.org/3.5/library/email.policy.html). Policy objects
allow precise control over how numerous features work when converting to
and from str or bytes. With the `email.policy.SMTP` the behavior of
email_as_bytes and email_as_string can be achieved using the builtin
`.as_string()` and `.as_bytes()` methods, without custom code or the
need to test it. Additionally these methods handle corner cases that we
don't currently handle, such as multi-part messages with different
encodings.

Fixes #1257

2 files changed, 3 insertions, 24 deletions

diff --git a/tests/db/utils_test.py b/tests/db/utils_test.py
index 23885067..7d50d888 100644
--- a/tests/db/utils_test.py
+++ b/tests/db/utils_test.py
@@ -8,6 +8,7 @@ import codecs
 import email
 import email.header
 import email.mime.application
+import email.policy
 import io
 import os
 import os.path
@@ -465,7 +466,7 @@ class TestMessageFromFile(TestCaseClassCleanup):
         text = b'This is some text'
         t = email.mime.text.MIMEText(text, 'plain', 'utf-8')
         _, sig = crypto.detached_signature_for(
-            helper.email_as_bytes(t), self.keys)
+            t.as_bytes(policy=email.policy.SMTP), self.keys)
         s = email.mime.application.MIMEApplication(
             sig, 'pgp-signature', email.encoders.encode_7or8bit)
         m = email.mime.multipart.MIMEMultipart('signed', None, [t, s])
@@ -555,7 +556,7 @@ class TestMessageFromFile(TestCaseClassCleanup):
         else:
             text = b'This is some text'
             t = email.mime.text.MIMEText(text, 'plain', 'utf-8')
-        enc = crypto.encrypt(helper.email_as_bytes(t), self.keys)
+        enc = crypto.encrypt(t.as_bytes(policy=email.policy.SMTP), self.keys)
         e = email.mime.application.MIMEApplication(
             enc, 'octet-stream', email.encoders.encode_7or8bit)
 
diff --git a/tests/helper_test.py b/tests/helper_test.py
index b47e5eff..b87d77af 100644
--- a/tests/helper_test.py
+++ b/tests/helper_test.py
@@ -383,28 +383,6 @@ class TestCallCmd(unittest.TestCase):
         self.assertEqual(code, 42)
 
 
-class TestEmailAsString(unittest.TestCase):
-
-    def test_empty_message(self):
-        message = email.message.Message()
-        actual = helper.email_as_string(message)
-        expected = '\r\n'
-        self.assertEqual(actual, expected)
-
-    def test_empty_message_with_unicode_header(self):
-        """Test if unicode header keys can be used in an email that is
-        converted to string with email_as_string()."""
-        # This is what alot.db.envelope.Envelope.construct_mail() currently
-        # does: It constructs a message object and then copies all headers from
-        # the envelope to the message object.  Some header names are stored as
-        # unicode in the envelope.
-        message = email.message.Message()
-        message[u'X-Unicode-Header'] = 'dummy value'
-        actual = helper.email_as_string(message)
-        expected = 'X-Unicode-Header: dummy value\r\n\r\n'
-        self.assertEqual(actual, expected)
-
-
 class TestShorten(unittest.TestCase):
 
     def test_lt_maxlen(self):