To reproduce:
1. Create a new project
2. Set the platform to Store apps and build
3. Delete the generated wsatestCertificate file
4. Build again - error is thrown "Copying file failed". The build has been prevented

To solve this you have to delete the temp, library and project settings folders and reopen the project.

Regression since 4.5.3p4

Workaround:
After deleting certificate file, there is no need to quit editor and delete project directories. Certificate easily can be re-created through player settings -> publishing settings.

But here are two issues:
1. Creating a new certificate in "publishing settings", certificate is always named "MetroTestCertificate";

2. If certificate is deleted, a proper message should appear instead of "can't copy certificate file...";