I've been porting content from one environment to another and have been getting an error that a dependency doesn't exist. We have all dependencies de-selected when porting, so this is expected.
The problem is that this dependency doesn't have an extension (like .dwt for Dreamweaver Template or .xml for a component), so the type of item isn't obvious. The import log is shown below:
2016/09/26 11:15:21 <236> [Information] Import process '051d95baf107480688dcb8a6c4dfda85' is started by 'CORP\prussell'.
2016/09/26 11:15:21 <236> [Information] Import started at 9/26/2016 11:15:21 AM.
2016/09/26 11:15:21 <236> [Information] Building list of items to import and determining required import actions.
2016/09/26 11:15:21 <236> [Information] Unzipping and initializing package for import.
2016/09/26 11:15:40 <236> [Error] Tridion.ContentManager.ImportExport.ImportExportException: Item '/webdav/030%20Content/Building%20Blocks/Content/z_test_content/z_test_folder' cannot be imported because it is absent on import TCM and its content was not exported to the package.
at Tridion.ContentManager.ImportExport.ToDoListInitializer.<>c__DisplayClassb.<SetImportActions>b__8()
at Tridion.ContentManager.ImportExport.Process.<>c__DisplayClass2.<InvokeInErrorHandler>b__1(Boolean isRetry)
at Tridion.ContentManager.ImportExport.SkipErrorHandler.Invoke[T](Func`2 function, LocalizableMessage message, Boolean retryAvailable, Boolean isCritical, UserReply additionalUserReplyOptions)
2016/09/26 11:15:40 <236> [Information] Failed action will be skipped.
2016/09/26 11:15:40 <236> [Error] Tridion.ContentManager.ImportExport.ImportExportException: The item '/webdav/030%20Content/Building%20Blocks/Content/z_test_content/z_test_folder/z_Test_Client_Information.xml' cannot be imported due to the fact that its dependency '/webdav/030%20Content/Building%20Blocks/Content/z_test_content/z_test_folder' cannot be imported.
2016/09/26 11:15:40 <236> [Information] Discovery of potential problems started at 9/26/2016 11:15:40 AM.
2016/09/26 11:15:40 <236> [Information] Import items into publication '030 Content' started at 9/26/2016 11:15:40 AM.
2016/09/26 11:15:49 <236> [Information] Import successfully finished at 9/26/2016 11:15:49 AM.
Import summary
Start time: 9/26/2016 11:15:21 AM
Finish time: 9/26/2016 11:15:49 AM
Total items imported: 1
New items created: 0
Existing items updated: 1
Items partially imported: 0
Items failed: 2
Updated items:
/webdav/030%20Content
Failed items:
/webdav/030%20Content/Building%20Blocks/Content/z_test_content/z_test_folder
/webdav/030%20Content/Building%20Blocks/Content/z_test_content/z_test_folder/z_Test_Client_Information.xml
2016/09/26 11:15:49 <236> [Information] Import process '051d95baf107480688dcb8a6c4dfda85' is finished.