I have some build.gradle file this 
buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.5.+'
    }
}
apply plugin: 'android'
dependencies {
    compile fileTree(dir: 'libs', include: '*.jar')
    compile 'com.github.chrisbanes.actionbarpulltorefresh:library:+'
}
android {
    compileSdkVersion 18
    buildToolsVersion '18'
    defaultConfig {
        targetSdkVersion 18
    }
    sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src']
            res.srcDirs = ['res']
        }
    }
}
that throws this error :
A problem occurred configuring root project 'NewsFeeder'.
> Failed to notify project evaluation listener.
   > Could not resolve all dependencies for configuration ':_DebugCompile'.
      > Could not find any version that matches com.github.chrisbanes.actionbarpulltorefresh:library:+.
        Required by:
            :NewsFeeder:unspecified
But, this reference to chrisbanes's actionbarpulltorefresh  seems to be correct : https://github.com/chrisbanes/ActionBar-PullToRefresh/wiki/QuickStart-Stock. How can it be since in this project is available in [maven central repo][1] ?
For information, I set in some local.propertiesfile sdk.dir=/home/adt-bundle-mac-x86_64-20130522/sdk, which is the same that what echo $ANDROID_SDK returns