No extensions after upgrade b3 -> b4

In PaperUI there are no extensions shown anymore. I get only some if I activate “include Experimental Extensions” or “include Legacy 1.x Bindings”

In the logfile I can see the following warning:

2016-09-16 10:14:51.786 [WARN ] [internal.service.FeaturesServiceImpl] - Can’t load features repository mvn:org.openhab.distro/openhab-aggregate-xml/2.0.0.b3/xml/features
java.io.IOException: Error resolving artifact org.openhab.distro:openhab-aggregate-xml:xml:features:2.0.0.b3: Could not find artifact org.openhab.distro:openhab-aggregate-xml:xml:features:2.0.0.b3 in oh-releases-repo (https://jcenter.bintray.com/) : mvn:org.openhab.distro/openhab-aggregate-xml/2.0.0.b3/xml/features
at org.apache.karaf.features.internal.service.RepositoryImpl.load(RepositoryImpl.java:96)[9:org.apache.karaf.features.core:4.0.4]
at org.apache.karaf.features.internal.service.RepositoryImpl.load(RepositoryImpl.java:85)[9:org.apache.karaf.features.core:4.0.4]
at org.apache.karaf.features.internal.service.FeaturesServiceImpl.getFeatures(FeaturesServiceImpl.java:637)[9:org.apache.karaf.features.core:4.0.4]
at org.apache.karaf.features.internal.service.FeaturesServiceImpl.listInstalledFeatures(FeaturesServiceImpl.java:682)[9:org.apache.karaf.features.core:4.0.4]
at org.openhab.core.karaf.internal.FeatureInstaller.isInstalled(FeatureInstaller.java:309)[162:org.openhab.core.karaf:2.0.0.b3]
at org.openhab.core.karaf.internal.FeatureInstaller.installFeature(FeatureInstaller.java:274)[162:org.openhab.core.karaf:2.0.0.b3]
at org.openhab.core.karaf.internal.FeatureInstaller.installPackage(FeatureInstaller.java:287)[162:org.openhab.core.karaf:2.0.0.b3]
at org.openhab.core.karaf.internal.FeatureInstaller.access$3(FeatureInstaller.java:283)[162:org.openhab.core.karaf:2.0.0.b3]
at org.openhab.core.karaf.internal.FeatureInstaller$1.run(FeatureInstaller.java:127)[162:org.openhab.core.karaf:2.0.0.b3]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)[:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)[:1.8.0_65]
at java.lang.Thread.run(Thread.java:745)[:1.8.0_65]
Caused by: java.io.IOException: Error resolving artifact org.openhab.distro:openhab-aggregate-xml:xml:features:2.0.0.b3: Could not find artifact org.openhab.distro:openhab-aggregate-xml:xml:features:2.0.0.b3 in oh-releases-repo (https://jcenter.bintray.com/)
at org.ops4j.pax.url.mvn.internal.AetherBasedResolver.resolve(AetherBasedResolver.java:626)[4:org.ops4j.pax.url.mvn:2.4.5]
at org.ops4j.pax.url.mvn.internal.AetherBasedResolver.resolve(AetherBasedResolver.java:570)[4:org.ops4j.pax.url.mvn:2.4.5]
at org.ops4j.pax.url.mvn.internal.AetherBasedResolver.resolve(AetherBasedResolver.java:548)[4:org.ops4j.pax.url.mvn:2.4.5]
at org.ops4j.pax.url.mvn.internal.AetherBasedResolver.resolve(AetherBasedResolver.java:523)[4:org.ops4j.pax.url.mvn:2.4.5]
at org.ops4j.pax.url.mvn.internal.Connection.getInputStream(Connection.java:123)[4:org.ops4j.pax.url.mvn:2.4.5]
at java.net.URL.openStream(URL.java:1038)[:1.8.0_65]
at org.apache.karaf.features.internal.service.RepositoryImpl.load(RepositoryImpl.java:91)[9:org.apache.karaf.features.core:4.0.4]
… 11 more
2016-09-16 10:14:51.863 [ERROR] [core.karaf.internal.FeatureInstaller] - Failed installing ‘openhab-package-standard’: No matching features for openhab-package-standard/0.0.0
2016-09-16 10:14:51.910 [ERROR] [core.karaf.internal.FeatureInstaller] - Failed installing ‘openhab-binding-exec’: No matching features for openhab-binding-exec/0.0.0
2016-09-16 10:14:52.032 [ERROR] [core.karaf.internal.FeatureInstaller] - Failed installing ‘openhab-binding-http’: No matching features for openhab-binding-http/0.0.0

It seems that it still looks for the extensions of b3.
But at bintray this folder is not existing anymore, see https://jcenter.bintray.com/org/openhab/distro/openhab-aggregate-xml/

How can I tell the system to look after b4 extensions?

Sounds similar to this. Unfortunately, there isn’t yet a working upgrade process from one beta to another.

Yes, that was the trick, just emptying the cache folders.