title: Invalid capabilities in alwaysMatch: unhandledPromptBehavior is type boolean instead of string
body: <p>I have upgraded my Selenium framework to the latest version. During execution of the code, I receive the following exception</p>
  
  <p><strong>Exception</strong>:</p>
  
  <pre><code>org.openqa.selenium.InvalidArgumentException: 
  Invalid capabilities in alwaysMatch: unhandledPromptBehavior is type boolean instead of string
  </code></pre>
  
  <p><strong>Details :</strong></p>
  
  <p>Selenium: 3.7.1
  IE : 3.7.0 (32 Bit Driver)
  java.version: '1.8.0_144'</p>
  
  <p>Automation code works with my older IE Driver (32 Bit) - 3.4.0. </p>
  
  <p>Please suggest your view to resolve the error .</p>
  
  <pre><code>capabilities.setCapability("UNHANDLED_PROMPT_BEHAVIOUR" ,false);
                      capabilities.setCapability(InternetExplorerDriver.INTRODUCE_FLAKINESS_BY_IGNORING_SECURITY_DOMAINS,true);
                      capabilities.setCapability(CapabilityType.ACCEPT_SSL_CERTS, true);
                      capabilities.setCapability(CapabilityType.SUPPORTS_ALERTS, true);
                      capabilities.setCapability(InternetExplorerDriver.UNEXPECTED_ALERT_BEHAVIOR, true);
                      capabilities.setCapability(InternetExplorerDriver.IE_ENSURE_CLEAN_SESSION, true);
                      capabilities.setCapability(InternetExplorerDriver.ENABLE_ELEMENT_CACHE_CLEANUP, true);
                      capabilities.setCapability("nativeEvents", false);
                      capabilities.setCapability("requireWindowFocus", false);
                      capabilities.setJavascriptEnabled(true);
                      capabilities.setCapability("ignoreProtectedModeSettings", true);
                      System.setProperty("webdriver.ie.driver", ieExe.getAbsolutePath());
                      opt = new InternetExplorerOptions();
                      opt.merge(capabilities);
                      driver = new InternetExplorerDriver(opt);
                      driver.manage().deleteAllCookies();
  driver.manage().window().maximize();
  </code></pre>