Bug 37709: Die and notify if file cannot be opened

Bug 37709: Die and notify if file cannot be opened

1 - perl misc/migration_tools/bulkmarcimport.pl -b --file=notafile.mrc -v
2 - Output:
    Characteristic MARC flavour: MARC21

    0 MARC records done in 0.00804400444030762 seconds
3 - Apply patch
4 - perl misc/migration_tools/bulkmarcimport.pl -b --file=notafile.mrc -v
5 - Output:
    Characteristic MARC flavour: MARC21
    Could not open notafile.mrc: No such file or directory at misc/migration_tools/bulkmarcimport.pl line 262.

Signed-off-by: Roman Dolny <roman.dolny@jezuici.pl>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>