Python，请求HTTP 415错误

Question

我（尝试）使用“请求”库通过Python发送以下内容：

import requests

 def Post_Value(date,time,dmg,pbxName,pbxDN,peakcalls,maxcalls,utilz,totalcalls):
    payload = '"<<<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">\
         <?xml version="1.0" encoding="utf-8" ?> \
         <s:Body> \
             <InsertSIPRecord xmlns="http://tempuri.org/"> \
            <applicationID>%s</applicationID> \
            <Date>%s</Date> \
            <TimeofPeakUsage>%s</TimeofPeakUsage> \
            <DMG>%s</DMG> \
            <PBXDN>%s</PBXDN> \
            <PBXName>%s</PBXName> \
            <PeakCalls>%s</PeakCalls> \
            <MaxConcurrentCalls>%s</MaxConcurrentCalls> \
            <PercentUtilization>%s</PercentUtilization> \
            <TotalCalls>%s</TotalCalls> \
            </InsertSIPRecord> \
    </s:Body> \
    </s:Envelope>>>'%(AppID,date,time,dmg,pbxDN,pbxName,peakcalls,maxcalls,utilz,totalcalls)
    try:
            r = requests.post(('http://%s'%host), data=payload)
    except Exception,e:
            msg += " %s \n   %s \n"%(Exception,e)
            print msg
            sys.exit()
    response= r.text
    return response

我收到415错误：

 HTTP/1.1 415 Cannot process the message because the content type 'application/octet-stream' was not the expected type 'text/xml; charset=utf-8'.\r\n

如何更改内容类型以符合预期？