The ipa command throws "Internal Server Error" when trying to add external member to IdM group in IPA AD trust setup.

Issue

• The ipa command throws "Internal Server Error" when trying to add external member to IdM group in IPA AD trust setup.

  # ipa group-add-member ad_users_external --external "TESTAD\Domain Users"
  
  [member user]: 
  [member group]: 
  ipa: ERROR: cannot connect to u'https://ipa.example.com/ipa/session/xml': Internal Server Error
  [root@ipa ~]# ipa -vv group-add-member ad_users_external --external "TESTAD\Domain Users"
  ipa: INFO: trying https://ipa.example.com/ipa/session/xml
  [member user]: 
  [member group]: 
  ipa: INFO: Forwarding 'group_add_member' to server u'https://ipa.example.com/ipa/session/xml'
  send: u'POST /ipa/session/xml HTTP/1.0\r\nHost: ipa.example.com\r\nAccept-Language: en-us\r\nReferer: https://ipa.example.com/ipa/xml\r\nCookie: ipa_session=bbb2f5edc8f8da3588c12f1b21c1e6bf;\r\nUser-Agent: xmlrpclib.py/1.0.1 (by www.pythonware.com)\r\nContent-Type: text/xml\r\nContent-Length: 658\r\n\r\n'
  send: "<?xml version='1.0' encoding='UTF-8'?>\n<methodCall>\n<methodName>group_add_member</methodName>\n<params>\n<param>\n<value><array><data>\n<value><string>ad_users_external</string></value>\n</data></array></value>\n</param>\n<param>\n<value><struct>\n<member>\n<name>raw</name>\n<value><boolean>0</boolean></value>\n</member>\n<member>\n<name>all</name>\n<value><boolean>0</boolean></value>\n</member>\n<member>\n<name>version</name>\n<value><string>2.46</string></value>\n</member>\n<member>\n<name>ipaexternalmember</name>\n<value><array><data>\n<value><string>ADTEST\\Domain Users</string></value>\n</data></array></value>\n</member>\n</struct></value>\n</param>\n</params>\n</methodCall>\n"
  reply: 'HTTP/1.1 500 Internal Server Error\r\n'
  header: Date: Thu, 07 Mar 2013 12:59:02 GMT
  header: Server: Apache/2.2.15 (Red Hat)
  header: Content-Length: 615
  header: Connection: close
  header: Content-Type: text/html; charset=iso-8859-1
  ipa: ERROR: cannot connect to u'https://ipa.example.com/ipa/session/xml': Internal Server Error