key [openstack-nova] not in the list of providers or apis: {}"

I get the an exception when I try to create a new context as below :
ComputeServiceContext context = ContextBuilder.newBuilder(provider)
.credentials(<username>, <password>)
.endpoint(<endpoint>).modules(modules)
.buildView(ComputeServiceContext.class);

Not sure what is wrong - the parameter provider is correct & all other parameters are correct as well.
I'm using maven with the following dependencies:

<dependency>
<groupId>org.jclouds.api</groupId>
<artifactId>openstack-nova</artifactId>
<version>1.6.0</version>
</dependency>

<dependency>
<groupId>org.jclouds.driver</groupId>
<artifactId>jclouds-slf4j</artifactId>
<version>1.6.0</version>
</dependency>