boot-qemu.py: Use more specific exception class

New pylint warns:

  boot-qemu.py:401:12: W0719: Raising too general exception: Exception (broad-exception-raised)
  boot-qemu.py:431:16: W0719: Raising too general exception: Exception (broad-exception-raised)

The type of exception really does not matter, as we do not expect this script
to be called, so the exception will never be caught. However, it is easy to
silence this by switching to a more specific exception. FileNotFoundError is
descriptive so use this exception to silence the warning.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Author: nathanchance

boot-qemu.py

@@ -398,7 +398,8 @@ def get_efi_args(guest_arch):
 
     for efi_img_location in efi_img_locations[guest_arch]:
         if efi_img_location is None:
-            raise Exception(f"edk2 could not be found for {guest_arch}!")
+            raise FileNotFoundError(
+                f"edk2 could not be found for {guest_arch}!")
         efi_img = Path("/usr/share", efi_img_location)
         if efi_img.exists():
             break
@@ -428,7 +429,7 @@ def get_efi_args(guest_arch):
         ]
         for efi_vars_location in efi_vars_locations:
             if efi_vars_location is None:
-                raise Exception("OVMF_VARS.fd could not be found!")
+                raise FileNotFoundError("OVMF_VARS.fd could not be found!")
             efi_vars = Path('/usr/share', efi_vars_location)
             if efi_vars.exists():
                 break