title: iOS SFHFKeychainUtils failing *sometimes* with error -25308 errSecInteractionNotAllowed
body: <p>I have this code getting back a password from the keychain for a given username NSString:</p>
  
  <pre><code>NSError *error = nil;
  NSString *appName = [[[NSBundle mainBundle] infoDictionary] objectForKey:(NSString*)kCFBundleNameKey];
  NSString *pw = [SFHFKeychainUtils getPasswordForUsername:username andServiceName:appName error:&amp;error];
  if(error != nil)
      // log the error    
  </code></pre>
  
  <p>Most of the time for most users this all works fine - but for some specific users this call seems to fail (and carry on failing) where it returns the following error:</p>
  
  <pre><code>The operation couldn’t be completed. (SFHFKeychainUtilsErrorDomain error -25308.)
  </code></pre>
  
  <p>This is apparently errSecInteractionNotAllowed - which from what I've read I <em>think</em> this means some kind of user interaction is required for the keychain to be accessed.</p>
  
  <p>Does anyone have any idea why this call may be failing for some specific users only? This keychain entry is specific to my app - so why would any user interaction be required to access it?</p>
  
  <p>Any pointers much appreciated...</p>