title: Cordova iOS plugin install pod install silently exits
body: <p>I am writing a script which automates the build of my Cordova App for iOS. 
  I'm using CLI 6.4.0 and cordova-ios 4.3.1 and I use the new possibility to add a framework to the plugin as a pod. Plugin is specified like this in the config.xml: </p>
  
  <pre><code>&lt;plugin name="sbb-cordova-plugin-onboarding" spec="~0.0.4" /&gt;
  </code></pre>
  
  <p>and the plugin uses a framework as pod: </p>
  
  <pre><code>&lt;framework src="SBBSMPLib" type="podspec"
      spec=":git =&gt; 'https://code.sbb.ch/scm/kd_cp/sbbsmplib-ios.git', :branch =&gt; 'develop'"/&gt;
  </code></pre>
  
  <p>My script runs well on my MacBook. There I get the following output </p>
  
  <pre><code>...
  
  Running `pod install` (to install plugins)
  Running command: pod install --verbose
  ==== pod install start ====
  
    Preparing
  
  ....
  </code></pre>
  
  <p>Now I'm trying to run the script on a Mac Server of our Jenkins infrastructure. There the plugin installation fails with the following log: </p>
  
  <pre><code>Discovered plugin "sbb-cordova-plugin-onboarding" in config.xml. Adding it to the project
  No scripts found for hook "before_plugin_add".
  Calling plugman.fetch on plugin "sbb-cordova-plugin-onboarding@~0.0.4"
  Fetching plugin "sbb-cordova-plugin-onboarding@~0.0.4" via npm
  Copying plugin "/Users/admin/.cordova/lib/npm_cache/sbb-cordova-plugin-onboarding/0.0.4/package" =&gt; "/Users/admin/jenkins-slave/workspace/kd.esta.mobile.hybrid.onboarding-testapp.ios.developer/apps/onboarding-testapp/plugins/sbb-cordova-plugin-onboarding"
  Calling plugman.install on plugin "/Users/admin/jenkins-slave/workspace/kd.esta.mobile.hybrid.onboarding-testapp.ios.developer/apps/onboarding-testapp/plugins/sbb-cordova-plugin-onboarding" for platform "ios
  Installing "sbb-cordova-plugin-onboarding" for ios
  Running command: /Users/admin/jenkins-slave/workspace/kd.esta.mobile.hybrid.onboarding-testapp.ios.developer/apps/onboarding-testapp/platforms/ios/cordova/version 
  Command finished with error code 0: /Users/admin/jenkins-slave/workspace/kd.esta.mobile.hybrid.onboarding-testapp.ios.developer/apps/onboarding-testapp/platforms/ios/cordova/version 
  Finding scripts for "before_plugin_install" hook from plugin sbb-cordova-plugin-onboarding on ios platform only.
  No scripts found for hook "before_plugin_install".
  Install start for "sbb-cordova-plugin-onboarding" on ios.
  Beginning processing of action stack for ios project...
  Action stack processing complete.
  Adding pods since the plugin contained &lt;framework&gt;(s) with type="podspec"
  pods.json: The file at /Users/admin/jenkins-slave/workspace/kd.esta.mobile.hybrid.onboarding-testapp.ios.developer/apps/onboarding-testapp/platforms/ios/pods.json does not exist.
  Creating new pods.json in platforms/ios
  Wrote to pods.json.
  Podfile: The file at /Users/admin/jenkins-slave/workspace/kd.esta.mobile.hybrid.onboarding-testapp.ios.developer/apps/onboarding-testapp/platforms/ios/Podfile does not exist.
  Creating new Podfile in platforms/ios
  Wrote to Podfile.
  Set pods.json for `SBBSMPLib`
  Added pod line for `SBBSMPLib`
  Wrote to pods.json.
  Wrote to Podfile.
  Running `pod install` (to install plugins)
  Failed to install 'sbb-cordova-plugin-onboarding':undefined
  Failed to restore plugin "sbb-cordova-plugin-onboarding" from config.xml. You might need to try adding it again. Error: Version should contain only numbers and dots
  Saving ios@4.3.1 into platforms.json
  No scripts found for hook "after_platform_add".
  </code></pre>
  
  <p>That is, 'pod install' does nothing. </p>
  
  <p>So I guess the problem has to do with the configuration of the Jenkins Mac Server. Any idea what is going wrong and how I can get a more detailed error?</p>
  
  <p>Thank</p>