When referencing 'net.sourceforge.argo:argo:2.25' as a compiletime dependency in my java project it get the following error:
[Fatal Error] argo-2.25.pom:3:10: Already seen doctype.
org.xml.sax.SAXParseException: Already seen doctype.
at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:246)
at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:284)
The xml looks rather decent: ( /Users/erikbroes/.gradle/caches/artifacts-14/filestore/net.sourceforge.argo/argo/2.25/pom/3c2dad469893c76856b74dcd0ce9a330f426961b/argo-2.25.pom )
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE project PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<project xmlns="http://maven.apache.org/POM/4.0.0">
<modelVersion>4.0.0</modelVersion>
<groupId>net.sourceforge.argo</groupId>
<artifactId>argo</artifactId>
<version>2.25</version>
<packaging>jar</packaging>
<name>Argo</name>
<description>Argo is an open source JSON parser and generator written in Java. It offers document, push, and pull APIs.</description>
<url>http://argo.sourceforge.net</url>
<licenses>
<license>
<name>The Apache Software License, Version 2.0</name>
<url>http://www.apache.org/licenses/LICENSE-2.0.txt</url>
<distribution>repo</distribution>
</license>
</licenses>
<scm>
<url>https://argo.svn.sourceforge.net/svnroot/argo/tags/2.25</url>
</scm>
<dependencies></dependencies>
<parent>
<groupId>org.sonatype.oss</groupId>
<artifactId>oss-parent</artifactId>
<version>7</version>
</parent>
</project>
When I remove the line with the <!DOCTYPE the problem 'resolves' itself, but that is quite a halfassed workaround 
(can't expect all devs to go change their gradle-cached dependencies) and I cannot really control what I download from a maven repo (of which I haven't set any so it should just get it from whereever is default).
Maven has no problems handling the file itself and seems to fetch it from http://repo.maven.apache.org/maven2/net/sourceforge/argo/argo/2.25/argo-2.25.pom
Maybe make the parsing of the pom files a bit less strict because unless someone changes the uploaded file there is no real workaround 