Kibana allows invalid plugin installation

[PhaedrusTheGreek]

In this example, shield-2.2.0.zip is not a valid Kibana plugin, downloaded from here

┌─╴╶╶ ╶      ╶
│ ~/Workspace/kibana-4.4.0-darwin-x64
├ $ bin/kibana plugin --install shield --url file:///tmp/shield-2.2.0.zip
Installing shield
Attempting to transfer from file:///tmp/shield-2.2.0.zip
Transferring 2155713 bytes....................
Transfer complete
Extracting plugin archive
Extraction complete
Optimizing and caching browser bundles...
Plugin installation complete

┌─╴╶╶ ╶      ╶
│ ~/Workspace/kibana-4.4.0-darwin-x64
├ $ bin/kibana
  log   [13:06:52.513] [warning][plugins] Skipping non-plugin directory at ~/Workspace/kibana-4.4.0-darwin-x64/installedPlugins/shield

[rashidkpc]

Given that there's no ill effect here, and a warning is logged, I'm going to file this as P3. I'd take a pull to fix it, but the current behavior isn't terrible.

[thomasneirynck]

Closing due to inactivity. This seems like a minor improvement for a fairly advanced operation, and current behavior is not that bad.