Fix flake8 issues

1) Drop unused import (fileinput)

Fixes:

| F401 'fileinput' imported but unused

2) Quoting from https://www.flake8rules.com/rules/E722.html:

| A bare except: clause will catch SystemExit and KeyboardInterrupt
| exceptions, making it harder to interrupt a program with Control-C, and
| can disguise other problems. If you want to catch all exceptions that
| signal program errors, use except Exception: (bare except is equivalent
| to except BaseException:).

Fixes:

| E722 	do not use bare except, specify exception instead

3) Quoting from https://www.flake8rules.com/rules/E713.html:

| Tests for membership should use the form x not in the_list rather than
| not x in the_list. The former example is simply more readable.

Fixes:

| E713 test for membership should be 'not in'