POSTing file to Jenkins fails

I'm trying to POST a file to Jenkins from Python, via multipart/form-data. The request body looks like this:

--===============1849003312==
Content-Type: application/octet-stream
Content-Transfer-Encoding: base64
Content-Disposition: file; name="file0"; filename="meta.xml"

PHhtbD4NCjwveG1sPg0K

--===============1849003312==--

This causes Jenkins to raise an exception on its end however, the most relevant bits of which follow:

Exception: <br>开发者_StackOverflow社区Stacktrace: <pre>org.apache.commons.fileupload.FileUploadException: Stream ended unexpectedly
   at org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:381)
   at org.apache.commons.fileupload.servlet.ServletFileUpload.parseRequest(ServletFileUpload.java:126)
   at org.kohsuke.stapler.RequestImpl.parseMultipartFormData(RequestImpl.java:767)
   at org.kohsuke.stapler.RequestImpl.getSubmittedForm(RequestImpl.java:782)

What's wrong with my POST request?

EDIT: The request headers are as follows:

Content-Type:

multipart/form-data; boundary="===============1849003312=="    

MIME-Version:

1.0

---

I believe the Content-Disposition: file; should be replaced with Content-Disposition: attachment;. The source code of FileUploadBase does not mention "file", and RFC 2183 does not list "file" as a value for content-disposition.