This is a missing dependency on ByteBuddy in the hibernate-osgi-5.2.6.Final-karaf.xml file. The workaround is to download the hibernate package, edit this file and drop in into the karaf deploy folder before installing the hibernate package. The required edit is adding the last line of the following snippet:

<features xmlns='http://karaf.apache.org/xmlns/features/v1.2.0' name='hibernate-osgi'>
<feature name='hibernate-orm' description='Combines all Hibernate core dependencies and required modules into a single feature' version='5.2.6.Final'>
<bundle>mvn:org.apache.servicemix.bundles/org.apache.servicemix.bundles.antlr/2.7.7_5</bundle>
<bundle>mvn:org.jboss.logging/jboss-logging/3.3.0.Final</bundle>
<bundle>mvn:net.bytebuddy/byte-buddy/1.5.13</bundle>

I've tested this under karaf 5.2.6. Pretty confident it will work for 5.2.5 as well.