URL tooltip test sheet:

<NOTE> All relative paths are based on the directory you were in when starting Manuskript. For Windows, it is assumed you started Manuskript from the C drive.

![https protocol absolute](https://www.rover.com/blog/wp-content/uploads/2018/11/dach1.jpg)
<WIN 10> SORTA FAIL: on PyQt 5.13 (Windows) this throws an error due to the supplied OpenSSL library being broken. Use PyQt<=5.12 to get this to work.
<UBUNTU 18.04.3> Works.

![http protocol absolute](http://i.imgur.com/rkBEbpc.jpg)
<WIN 10> <UBUNTU 18.04.3> Works.

![file protocol drive absolute](file:C:/Portable/Manuskript/icons/Manuskript/icon-512px.png)
![file protocol / drive absolute](file:/C:/Portable/Manuskript/icons/Manuskript/icon-512px.png)
![file protocol // drive absolute](file://C:/Portable/Manuskript/icons/Manuskript/icon-512px.png)
![file protocol /// drive absolute](file:///C:/Portable/Manuskript/icons/Manuskript/icon-512px.png)
<WIN 10> NOTE: all work except for two slashes: file://C:/... does NOT work.
Error message: The network path was not found.
<UBUNTU 18.04.3> All fail as expected. (Because of drive letters.) But double-slashes is still the odd one out: we need to specially handle this case to prevent it from getting stuck in the processing pipeline.

![file protocol no-drive absolute](file:test_root.jpg)
<WIN 10> The system cannot find the file specified. (As expected: relative path.)
<UBUNTU 18.04.3> No such file or directory.
![file protocol / no-drive absolute](file:/test_root.jpg)
<WIN 10> <UBUNTU 18.04.3> Works.
![file protocol // no-drive absolute](file://test_root.jpg)
<WIN 10> The specified path is invalid.
<UBUNTU 18.04.3> Request for opening non-local file.
![file protocol /// no-drive absolute](file:///test_root.jpg)
<WIN 10> Works.
<UBUNTU 18.04.3> Works.

![no protocol drive local absolute](C:\test_root.jpg)
<WIN 10> Works as expected.
<UBUNTU 18.04.3> Special handling: The protocol "c" is not supported. (Was not expected to work on Linux anyways, and without special handling it also fails.)
Note: Qt really messes up our logic here, so it is important we manually handle this scenario.

![no protocol drive absolute quoted]("C:\test_root.jpg")
<WIN 10> The newly added utterly-bogus error message.
<UBUNTU 18.04.3> The newly added utterly-bogus error message. (Was never expected to work.)

![no protocol no-drive absolute](\test_root.jpg)
<WIN 10> Works as expected.
<UBUNTU 18.04.3> The newly added utterly-bogus error message.

![no protocol absolute](/test_root.jpg)
<WIN 10> <UBUNTU 18.04.3> Works.

![no protocol relative no dot](icons\Manuskript\icon-512px.png)
![no protocol relative with dot](./icons/Manuskript/icon-512px.png)
<WIN 10> <UBUNTU 18.04.3> The newly added utterly-bogus error message.

![file protocol relative no dot](file:icons/Manuskript/icon-512px.png)
![file protocol relative with dot](file:./icons/Manuskript/icon-512px.png)
<WIN 10> <UBUNTU 18.04.3> Works.

![file protocol /// relative](file:///icons/Manuskript/icon-512px.png)
<WIN 10> <UBUNTU 18.04.3> Fails as expected. Cannot find the path specified.