`FileNotFoundError` not raised correctly

[raimund-schluessler]

@paulmueller If I am not wrong, the FileNotFoundError and its variant are not raised correctly. errno.ENOENT and filename are missing here:

impose/impose/data.py

Line 87 in 5b2907b

raise FileNotFoundError(f"File does not exist: '{self.path}'")

impose/impose/session.py

Lines 279 to 284 in 5b2907b

	raise ImposeDataFileNotFoundError(
	name,
	"Could not find file '{}'".format(name)
	+ (f" (sig '{signature}')" if signature is not None else "")
	+ "!"
	)