lfs: explicitly add the Content-Length header when uploading blobs, for py3 This was the reason for test-lfs-test-server.t#git-server complaining about an "invalid byte in chunk length". For some reason if this isn't explicitly added, py3.7.1 is adding `transfer-encoding: chunked` as well as `Content-length: x`. Wireshark flagged this as malformed. However, if this is set, it doesn't bother with `transfer-encoding`. Before this patch with py3: PUT /objects/31cf46fbc4ecd458a0943c5b4881f1f5a6dd36c53d6167d5b69ac45149b38e5b HTTP/1.1 Accept-Encoding: identity Content-length: 12 accept: application/vnd.git-lfs content-type: application/octet-stream host: localhost:20062 transfer-encoding: chunked user-agent: git-lfs/2.3.4 (Mercurial 4.9rc0+149-7eb7637e34bf) Before this patch with py27: PUT /objects/31cf46fbc4ecd458a0943c5b4881f1f5a6dd36c53d6167d5b69ac45149b38e5b HTTP/1.1 Accept-Encoding: identity accept: application/vnd.git-lfs content-type: application/octet-stream content-length: 12 host: localhost:20062 user-agent: git-lfs/2.3.4 (Mercurial 4.9rc0+149-7eb7637e34bf+20190128) With this patch and py3, the content is the same as the py27 example. RFC2616 says to ignore `Content-Length` if `Transfer-Encoding` is present, so maybe there's nothing to do in the hg-server side (though I'm not sure which it is using if presented both). Maybe chunked encoding is better to do? If someone knows how to suppress the `Content-Length`, we can try that instead.