Shell: Add file system browser to retrieve arbitrary files

spec/lib/file_tree_spec.rb

@@ -161,7 +161,7 @@ describe FileTree do
     end
 
     context 'with leaf nodes' do
-      let(:node) { root.add(Tree::TreeNode.new('')) }
+      let(:node) { root.add(Tree::TreeNode.new('', CodeOcean::File.new)) }
 
       it 'is a file icon' do
         expect(file_tree).to receive(:file_icon)

spec/views/execution_environments/shell.html.slim_spec.rb

@@ -12,6 +12,6 @@ describe 'execution_environments/shell.html.slim' do
 
   it 'contains the required data attributes' do
     expect(rendered).to have_css('#shell[data-message-timeout]')
-    expect(rendered).to have_css("#shell[data-url='#{execute_command_execution_environment_path(execution_environment)}']")
+    expect(rendered).to have_css("#shell[data-id='#{execution_environment.id}']")
   end
 end