title: QuickFIX remove tag from logon process
body: <p>I'm using QuickFIX and Python to initiate a connection to a fixserver process which handles FIX5.0SP2. When I'm trying to initiate a connection I receive a disconnect after getting the following message: <code>(Message 1 Rejected: Required tag missing:1137)</code>. 
  This tag is not mandatory by my fixserver process and I'm trying to remove it from the logon process. I removed it from the FIXT11.xml and created a custom xml for this but without any success. Do I miss something? I thought you can easily switch them from mandatory to non-mandatory in this file?</p>
  
  <p>Here is my config:</p>
  
  <pre><code>[DEFAULT]
  ConnectionType=initiator
  ReconnectInterval=60
  DefaultApplVerID=FIX.5.0SP2
  UseDataDictionary=N
  ResetOnLogout=Y
  ResetOnLogon=Y
  AppDataDictionary=/home/foo/Documents/QuickFix/fix_specs/FIX50SP2CustomTags.xml
  TransportDataDictionary=/home/foo/Documents/QuickFix/fix_specs/FIXT11CustomTags.xml
  
  [SESSION]
  BeginString=FIXT.1.1
  ConnectionType=initiator
  SenderCompID=FIXSRV
  TargetCompID=RTD
  ReconnectInterval=30
  HeartBtInt=30
  StartTime=00:30:00
  EndTime=23:30:00
  SocketConnectProtocol=TCP
  SocketConnectPort=1284
  SocketConnectHost=X.X.X.X
  FileStorePath=/home/foo/Documents/QuickFix/data
  FileLogPath=/home/foo/Documents/QuickFix/logs
  ValidateFieldsOutOfOrder=N
  ValidateFieldsHaveValues=N
  #ValidateUserDefinedFields=N`
  </code></pre>
  
  <p>Here is the quickfix output with fix message:</p>
  
  <pre><code>&lt;20170213-12:52:41.812, FIXT.1.1:FIXSRV-&gt;RTD, event&gt;
    (Created session)
  &lt;20170213-12:52:41.813, FIXT.1.1:FIXSRV-&gt;RTD, event&gt;
    (Connecting to X.X.X.X on port 1284)
  Sent the Admin following message: 8=FIXT.1.1|9=77|35=A|34=1|49=FIXSRV|52=20170213-12:52:41.816|56=RTD|98=0|108=30|141=Y|1137=9|10=140|
  &lt;20170213-12:52:41.817, FIXT.1.1:FIXSRV-&gt;RTD, outgoing&gt;
    (8=FIXT.1.1|9=106|35=A|34=1|49=FIXSRV|52=20170213-12:52:41.816|56=RTD|50=FIX50|98=0|108=30|141=Y|553=FIX50|554=fix50|1137=9|10=083|)
  &lt;20170213-12:52:41.817, FIXT.1.1:FIXSRV-&gt;RTD, event&gt;
    (Initiated logon request)
  &lt;20170213-12:52:41.820, FIXT.1.1:FIXSRV-&gt;RTD, incoming&gt;
    (8=FIXT.1.1|9=000106|35=A|1128=7|49=RTD|56=FIXSRV|34=1|50=FIX50|52=20170213-12:52:41.639|98=0|108=30|141=Y|553=FIX50|554=fix50|10=228|)
  &lt;20170213-12:52:41.820, FIXT.1.1:FIXSRV-&gt;RTD, event&gt;
    (Message 1 Rejected: Required tag missing:1137)
  &lt;20170213-12:52:41.820, FIXT.1.1:FIXSRV-&gt;RTD, event&gt;
    (Tried to send a reject while not logged on)
  &lt;20170213-12:52:41.820, FIXT.1.1:FIXSRV-&gt;RTD, event&gt;
    (Required field missing from logon)
  &lt;20170213-12:52:41.820, FIXT.1.1:FIXSRV-&gt;RTD, event&gt;
    (Disconnecting)
  </code></pre>
  
  <p>Update:
  I tried to change that field <code>&lt;field name='DefaultApplVerID' required='Y'/&gt;</code> to <code>required='N'</code> in my dictionary but without any effect. Other fields are possible to change them to non-mandatory and they are skipped when not set. Is this specific mandatory fix 5.0SP2 field hard coded and can't be non-mandatory?</p>