log more information about what is happening for this error

Test-Plan:
N/A

refs: ADMIN-1573

Change-Id: I63e89be04aa0ded86470b7fefb3cc56d35c4992f
Reviewed-on: https://gerrit.instructure.com/172244
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Rex Fleischer <rfleischer@instructure.com>
Product-Review: Rex Fleischer <rfleischer@instructure.com>

gems/canvas_unzip/lib/canvas_unzip.rb

@@ -136,7 +136,7 @@ class CanvasUnzip
         raise UnknownArchiveType, "invalid tar"
       end
     else
-      raise UnknownArchiveType, "unknown mime type #{mime_type}"
+      raise UnknownArchiveType, "unknown mime type #{mime_type} for archive #{File.basename(archive_filename)}"
     end
   end
 

spec/lib/canvas/migration_spec.rb

@@ -77,7 +77,7 @@ describe "Migration package importers" do
       archive = Canvas::Migration::Archive.new(settings)
       expect{
         Canvas::Migration::PackageIdentifier.new(archive).identify_package
-      }.to raise_error(Canvas::Migration::Error, "Error identifying package type: unknown mime type text/plain")
+      }.to raise_error(Canvas::Migration::Error, "Error identifying package type: unknown mime type text/plain for archive invalid.zip")
     end
   end