Permission error that may occur on Windows platforms

[Andvinsa]

We've been using this plugin in a project with many PlantUML images. During today's build, we encountered a high probability of a permission error occurring around line 414 of the render function during os.rename. Theoretically, permissions should be released after f.close(), but I'm unsure why this issue persists. In any case, adding a brief time.sleep() delay after f.close() resolved the problem.

[Andvinsa]

Though it's not a very elegant solution