Unable to load class 'org.codehaus.groovy.runtime.StringGroovyMethods'.

Got this error upon building the lib:

``` groovy
Error: Unable to load class 'org.codehaus.groovy.runtime.StringGroovyMethods'.
Possible causes for this unexpected error include:

• Gradle's dependency cache
  may be corrupt (this sometimes occurs after a network connection timeout.)
  Re-download dependencies and sync project
  (requires network)
• The state of a Gradle build process (daemon)
  may be corrupt. Stopping all Gradle daemons may solve this problem.
  Stop Gradle build processes (requires restart)
  
• Your project may be using a third-party plugin which is not
  compatible with the other plugins in the project or the version of Gradle
  requested by the project.

In the case of corrupt Gradle processes,
you can also try closing the IDE and then killing all Java processes.
```

My internet is connected while building....

thanks