Auth fail when ssh-agent = true

Environment info

gradle-ssh-plugin-2.7.0 (groovy-ssh-2.7.0, jsch-0.1.53, groovy-2.4.7, java-1.8.0_77)

Steps to reproduce

1. Configure remotes with SSH agent.
2. Write a deploy task with an arbitrary session.
3. Run deploy task.

plugins {
    id 'org.hidetake.ssh' version '2.7.0'
}

remotes {
    does_work {
        host = 'host'
        user = 'alex_ordonez'
        agent = true
//      passphrase = 'dontpostmeonline'
        identity = file("${System.properties['user.home']}/.ssh/id_rsa")
    }
    does_not_work {
        host = 'host'
        user = 'alex_ordonez'
//      agent = true
        passphrase = 'dontpostmeonline'
        identity = file("${System.properties['user.home']}/.ssh/id_rsa")
    }
}

The output from Gradle is:

Session #2 failed: java.lang.RuntimeException: java.lang.RuntimeException: com.jcraft.jsch.JSchException: Auth fail
:deploy FAILED

FAILURE: Build failed with an exception.

* Where:
Build file '/Users/alex/projects/project/build.gradle' line: 78 // Line with ssh.run in deploy task

* What went wrong:
Execution failed for task ':deploy'.
> 1 of 2 session (50%) failed

BUILD FAILED

Start with the build.gradle deploy task and the remotes configuration shown in the report, then reproduce the failure with agent = true and the SSH agent environment. Compare it with the working passphrase configuration; done means the deploy task authenticates successfully through the agent without an Auth fail.