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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Multipart Emails: Python2 bug","articleBody":"A bug in `future.backports.email.Message.set_boundary` causes errors when serializing multipart email Message objects.\r\n\r\nUsing Python 2.7.15, here is output from serializing a multipart email:\r\n```console\r\n\u003e\u003e\u003e import future.backports.email as email\r\n\u003e\u003e\u003e import future.backports.email.mime.multipart\r\n\u003e\u003e\u003e m = email.mime.multipart.MIMEMultipart()\r\n\u003e\u003e\u003e m.as_string()\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/usr/local/lib/python2.7/site-packages/future/backports/email/message.py\", line 155, in as_string\r\n    g.flatten(self, unixfrom=unixfrom)\r\n  File \"/usr/local/lib/python2.7/site-packages/future/backports/email/generator.py\", line 118, in flatten\r\n    self._write(msg)\r\n  File \"/usr/local/lib/python2.7/site-packages/future/backports/email/generator.py\", line 190, in _write\r\n    self._write_headers(msg)\r\n  File \"/usr/local/lib/python2.7/site-packages/future/backports/email/generator.py\", line 216, in _write_headers\r\n    for h, v in msg.raw_items():\r\n  File \"/usr/local/lib/python2.7/site-packages/future/backports/email/message.py\", line 446, in raw_items\r\n    return iter(self._headers.copy())\r\nAttributeError: 'list' object has no attribute 'copy'\r\n```\r\n\r\nAnother example indicating the source of the bug:\r\n```console\r\n\u003e\u003e\u003e import future.backports.email as email\r\n\u003e\u003e\u003e import future.backports.email.mime.multipart\r\n\u003e\u003e\u003e m = email.mime.multipart.MIMEMultipart()\r\n\u003e\u003e\u003e type(m._headers)\r\n\u003cclass 'future.types.newlist.newlist'\u003e\r\n\u003e\u003e\u003e m.set_boundary('===============6387699881409002085==')\r\n\u003e\u003e\u003e type(m._headers)\r\n\u003ctype 'list'\u003e\r\n```","author":{"url":"https://github.com/seshrs","@type":"Person","name":"seshrs"},"datePublished":"2019-01-19T03:54:12.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/429/python-future/issues/429"}