DFetch doesn't warn if patch file doesn't exist

[ben-edna]

In

dfetch/dfetch/project/vcs.py

Line 107 in 7040a16

if self.__project.patch and os.path.exists(self.__project.patch):

is checked if the patch file exist, but if the path is incorrect, DFetch silently continuous.

Maybe something along the lines of:

if self.__project.patch:
    if os.path.exists(self.__project.patch):
        self.apply_patch()
    else:
        logger.warning(f"Skipping non-existent patch {self.__project.patch}")