Better method for managing python black package

We are able to call `black` by shelling out to it on the system path, and we are able to cache its results by enforcing a version check on the binary. However, if it isn't on the path, or the version is wrong, we just show a helpful error message and let the user figure it out from there:

https://github.com/diffplug/spotless/blob/608e128381c89260f8a38fba985415c1f962ec7b/lib/src/main/java/com/diffplug/spotless/python/BlackStep.java#L65-L66

It would be nice if we could handle this better, or at least have better instructions. There are a few python plugins in the gradle ecosystem, I'll reach out to them to see if they are interested.

Comienza con BlackStep.java en las líneas enlazadas para entender la búsqueda actual de la ruta del sistema, la comprobación de la versión y el mensaje de error. Revisa los Gradle Python plugins mencionados antes de elegir un enfoque; se considera terminado cuando las instalaciones de Black que faltan o son incompatibles se gestionan mejor o tienen instrucciones más claras.

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