Failed to move hack into script plugin

I added an (experimental) hack to one of the android plugin’s tasks using metaprogramming. This works as long as I put it inside my build.gradle. I would like to move it into a separate script that I then apply though. This does fail with some “property not found” error, seems the class I reference can not be resolved.

Do scripts load from a different classpath (seems the class can not be resolved)? And is there a away to make this work?

Here is the hack:

// amend task "signingReport" to show base64-encoded hashes (as needed for app registration at Facebook)
def signingTaskMetaClass = com.android.build.gradle.internal.tasks.SigningReportTask.metaClass
if (!signingTaskMetaClass.properties.find { it.name == 'enhanced' }) {
  signingTaskMetaClass.enhanced = true
  MetaMethod metaFinger = signingTaskMetaClass.getStaticMetaMethod('getFingerprint', java.security.cert.Certificate, String)
  signingTaskMetaClass.static.getFingerprint = { java.security.cert.Certificate cert, String hashAlgorithm ->
    def base64 = java.security.MessageDigest.getInstance(hashAlgorithm).digest(cert.encoded).encodeBase64()
    metaFinger.invoke(delegate, cert, hashAlgorithm) + "\n$hashAlgorithm (base64): $base64"
  }
}

And this is the error when applied from a separate file (via apply from:) :

Could not find property 'com' on project ':mobile'.