FileSize validator reads the entire file into memory

[Zverik]

I'm looking at this line and either my understanding of Python is lacking, or it does len(file.read()), effectively reading the entire contents of a file into a string variable, then measuring its length, and discarding it.

Shouldn't there be more effective and less memory-consuming ways of getting a file size?

[azmeuk]

Hello. Thank you for noticing this.
Indeed this part could probably be improved. Feel free to open a PR!