pom.xml file with 'packaging: aar' not resolved, returns 0 exit value

[jpopelka]

$ wget http://repo1.maven.org/maven2/de/halfbit/tinybus/2.0.0/tinybus-2.0.0.pom -O pom.xml
$ MERCATOR_JAVA_RESOLVE_POMS=true mercator pom.xml; echo $?
{
   "versions": {
      "Java-POM": "2c485843a7428d3e39488382f875c0d7b47b4050"
   },
   "items": [
      {
         "time": "2017-10-04T15:48:24.817529438+02:00",
         "path": "/home/jpopelka/Documents/pom.xml",
         "ecosystem": "Java-POM",
         "digests": {
            "manifest": "c063a53aed023a45523dc80a85037bcc18760a43"
         }
      }
   ]
}
0

$ mercator pom.xml
{
   "versions": {
      "Java-POM": "2c485843a7428d3e39488382f875c0d7b47b4050"
   },
   "items": [
      {
         "time": "2017-10-04T15:47:40.567456215+02:00",
         "path": "/home/jpopelka/Documents/pom.xml",
         "ecosystem": "Java-POM",
         "result": {
            "pom.xml": {
               "artifactId": "tinybus",
               "dependencies": {},
               "description": "A lightweight and simple event bus tailored for Android",
               "groupId": "de.halfbit",
               "licenses": [
                  "The Apache Software License, Version 2.0"
               ],
               "name": "TinyBus Library",
               "scm_url": "https://github.com/beworker/tinybus",
               "url": "https://github.com/beworker/tinybus",
               "version": "2.0.0"
            }
         },
         "digests": {
            "manifest": "c063a53aed023a45523dc80a85037bcc18760a43"
         }
      }
   ]
}

[jpopelka]

$ mvn help:effective-pom
[INFO] Scanning for projects...
[ERROR] [ERROR] Some problems were encountered while processing the POMs:
[ERROR] Unknown packaging: aar @ line 8, column 14
 @ 
[ERROR] The build could not read 1 project -> [Help 1]
[ERROR]   
[ERROR]   The project de.halfbit:tinybus:2.0.0 (/home/jpopelka/Documents/pom.xml) has 1 error
[ERROR]     Unknown packaging: aar @ line 8, column 14

mercator should return non-zero exit status in that case, which it doesn't