Expression Translation Error when Publishing SharePoint Workflow

When publishing the workflow with

client.PublishWorkflow(workflowName, "MyWorkflow.xaml");

you may notice ExpressionTranslation Errors. Usually these errors briefly explain the problem. Unfortunately there is one strange case, which is difficult to explain.
To understand this take a look on following picture:

Interestingly, you will probably in this case notice that you even don’t have this file. Why then, translator is training to load some not existing file?
The problem here is the name of the path. ..\\External Variables\\C# (not shown in the error message, because expression translator cannot read it).
C# is the part of path which cannot be used. To workaround this issue, copy your project to any more human readable path and all will work.

Please also note, sometimes some workflow on the same path do not have this issue. These are probably VB-Expression based workflows, which comes from version 4.0 of Workflow Foundation.
That means this problem will happen on WF 4.5 C# workflows only.