I do not think this causes any functional problems, but it can be a little
unsettling to see warnings on the karaf console just by installing
features.

one way to reproduce with latest (as of 7/20) Boron snapshot distribution:

start karaf:

opendaylight-user@root>repo-add mvn:org.opendaylight.integration/features-integration-test/0.5.0-SNAPSHOT/xml/features
Adding feature url mvn:org.opendaylight.integration/features-integration-test/0.5.0-SNAPSHOT/xml/features
opendaylight-user@root>feature:install odl-integration-compatible-with-all
Refreshing bundles org.apache.sshd.core (30)
opendaylight-user@root>Warning: org.apache.xerces.parsers.SAXParser: Feature 'http://javax.xml.XMLConstants/feature/secure-processing' is not recognized.
Warning: org.apache.xerces.parsers.SAXParser: Property 'http://javax.xml.XMLConstants/property/accessExternalDTD' is not recognized.
Warning: org.apache.xerces.parsers.SAXParser: Property 'http://www.oracle.com/xml/jaxp/properties/entityExpansionLimit' is not recognized.
Warning: org.apache.xerces.parsers.SAXParser: Property 'http://javax.xml.XMLConstants/property/accessExternalDTD' is not recognized.
Warning: org.apache.xerces.parsers.SAXParser: Property 'http://www.oracle.com/xml/jaxp/properties/entityExpansionLimit' is not recognized.

opendaylight-user@root>