We use the JClouds plugin to provision OpenNebula instances via aws-ec2 api
Since update to 2.28 the connection fails.

From the stack trace i guess this is related to JENKINS-38736

Cannot connect to specified cloud, please check the identity and credentials: Unable to create injector, see the following errors:

1) Overriding @Provides methods is not allowed.
@Provides method: org.jclouds.logging.config.LoggingModule.createLoggerFactory()
overridden by: jenkins.plugins.jclouds.compute.JCloudsCloud$1.createLoggerFactory()
at com.google.inject.internal.ProviderMethodsModule.getProviderMethods(ProviderMethodsModule.java:163)

2) Overriding @Provides methods is not allowed.
@Provides method: org.jclouds.compute.config.BaseComputeServiceContextModule.provideTemplateOptions()
overridden by: org.jclouds.aws.ec2.compute.config.AWSEC2ComputeServiceContextModule.provideTemplateOptions()
at com.google.inject.internal.ProviderMethodsModule.getProviderMethods(ProviderMethodsModule.java:163)

3) Overriding @Provides methods is not allowed.
@Provides method: org.jclouds.compute.config.BaseComputeServiceContextModule.provideImageExtension()
overridden by: org.jclouds.aws.ec2.compute.config.AWSEC2ComputeServiceContextModule.provideImageExtension()
at com.google.inject.internal.ProviderMethodsModule.getProviderMethods(ProviderMethodsModule.java:163)

4) Overriding @Provides methods is not allowed.
@Provides method: org.jclouds.compute.config.BaseComputeServiceContextModule.provideSecurityGroupExtension()
overridden by: org.jclouds.aws.ec2.compute.config.AWSEC2ComputeServiceContextModule.provideSecurityGroupExtension()
at com.google.inject.internal.ProviderMethodsModule.getProviderMethods(ProviderMethodsModule.java:163)