title: CloudKit Error when modifying CKRecords: "Zone Busy"
body: <p>Here's a snippet of code in which I'm modifying some records on a user's private CloudKit DB.</p>
  
  <pre><code>    let op = CKModifyRecordsOperation(recordsToSave: recordsToModify, recordIDsToDelete: [])
      op.savePolicy = CKRecordSavePolicy.ChangedKeys
      op.modifyRecordsCompletionBlock = { saved, deleted, err in
          println("modified all ... \(saved.count) w err '\(err)' \(err != nil ? err.userInfo : [:])")
      }
      self.privateDB.addOperation(op)
  </code></pre>
  
  <p>Νοrmally this works great:</p>
  
  <pre><code> modified all ... 284 w err 'nil' Optional([:])
  </code></pre>
  
  <p>But every now and then I get the following output:</p>
  
  <pre><code> modified all ... 0 w err '&lt;CKError 0x7f9210e92840:"Zone Busy" (23/2029);
      "Zone busy"&gt;' Optional([NSDebugDescription: CKInternalErrorDomain: 2029,
      NSLocalizedDescription: Zone busy, NSUnderlyingError: &lt;CKError 0x7f9210ea7dd0:
      "Unknown Error" (2029)&gt;])
  </code></pre>
  
  <p>I'm assuming this is a hiccup of some sort on CloudKit's side of things - but how do I detect this? How should I handle it?</p>