I try to upgrade from 2.14.1-01 to 3.1.0-04. When I invoke upgrade I got: 
The nexus 2 log contains the following:
2016-11-22 15:06:21 INFO [pxpool-1-thread-14] *TASK com.sonatype.nexus.migrationagent.repository.RepositoryMigrationTask - Scheduled task (RepositoryMigrationTask) canceled :: Upgrading repository: vaadin-addons (started 2016-11-22T15:06:19+03:00, runtime 0:00:01.710) 2016-11-22 15:06:21 INFO [pxpool-1-thread-14] *TASK org.sonatype.nexus.configuration.application.DefaultNexusConfiguration - Applying Nexus Configuration due to changes in [Scheduled Tasks] made by *TASK... 2016-11-22 15:06:22 WARN [qtp10032359-104] *UNKNOWN org.sonatype.sisu.siesta.server.internal.mappers.ThrowableExceptionMapper - java.lang.NullPointerException: Cannot invoke method extract() on null object java.lang.NullPointerException: Cannot invoke method extract() on null object at org.codehaus.groovy.runtime.NullObject.invokeMethod(NullObject.java:91) ~[na:na] at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:48) ~[na:na] at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48) ~[na:na] at org.codehaus.groovy.runtime.callsite.NullCallSite.call(NullCallSite.java:35) ~[na:na] at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48) ~[na:na] at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:57) ~[na:na] at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125) ~[na:na] at com.sonatype.nexus.migrationagent.rest.RepositoryChangelogResource$_get_closure1$_closure2.doCall(RepositoryChangelogResource.groovy:115) ~[na:na]
( I have published the full stack trace here http://pastebin.com/byjfeC8L )
Could you please show me the way to fix this problem?
Thanks in advance!
