HTTPCLIENT-1073: receiving a 206 (Partial Content) response to a request that did not request partial content is problematic from a cache perspective, so throwing a ClientProtocolException is ok. However, we should properly consume the body of the 206 response before throwing the exception to ensure that resources are properly released.
httpcomponents/httpclient/trunk/httpclient-cache/src/main/java/org/apache/http/impl/client/cache/ResponseProtocolCompliance.java