Fix issues discovered by common python linters

Fix some issues discovered by common python linters including:
* switch `None` comparisons to use `is` rather than `==`. Identity !=
equality, and I've spent 40+ hours before tracking down a subtle bug
caused by exactly this issue. Note that this may introduce a problem if
one of the scripts is depending on this behavior, in which case the
comparison should be changed to `True`/`False` rather than `None`.
* Use `except Exception:` as bare `except:` statements have been
discouraged for years. Ideally for some of these we'd examine if there
were specific exceptions that should be caught, but for now I simply
caught all. Again, this could introduce very subtle behavioral changes
under Python 2, but IIUC, that was all fixed in Python 3, so safe to
move to `except Exception:`.
* Use more idiomatic `if not x in y`--> `if x not in y`
* Use more idiomatic 2 blank lines. I only did this at the beginning,
until I realized how overwhelming this was going to be to apply, then I
stopped.
* Add a TODO where an undefined function name is called, so will fail
whenever that code is run.
* Add more idiomatic spacing around `:`. This is also only partially
cleaned up, as I gave up when I saw how `asn2wrs.py` was clearly
infatuated with the construct.
* Various other small cleanups, removed some trailing whitespace and
improper indentation that wasn't a multiple of 4, etc.

There is still _much_ to do, but I haven't been heavily involved with
this project before, so thought this was a sufficient amount to put up
and see what the feedback is.

Linters that I have enabled which highlighted some of these issues
include:
* `pylint`
* `flake8`
* `pycodestyle`

1 files changed, 5 insertions, 5 deletions

diff --git a/tools/check_tfs.py b/tools/check_tfs.py
index a9b9097abe..89581d00f0 100755
--- a/tools/check_tfs.py
+++ b/tools/check_tfs.py
@@ -88,7 +88,7 @@ def findItems(filename):
 
 
 
-def isDissectorFile(filename):
+def is_dissector_file(filename):
     p = re.compile('.*packet-.*\.c')
     return p.match(filename)
 
@@ -99,7 +99,7 @@ def findDissectorFilesInFolder(folder):
     for f in sorted(os.listdir(folder)):
         if should_exit:
             return
-        if isDissectorFile(f):
+        if is_dissector_file(f):
             filename = os.path.join(folder, f)
             files.append(filename)
     return files
@@ -160,20 +160,20 @@ elif args.commits:
     files = [f.decode('utf-8')
              for f in subprocess.check_output(command).splitlines()]
     # Will examine dissector files only
-    files = list(filter(lambda f : isDissectorFile(f), files))
+    files = list(filter(lambda f : is_dissector_file(f), files))
 elif args.open:
     # Unstaged changes.
     command = ['git', 'diff', '--name-only']
     files = [f.decode('utf-8')
              for f in subprocess.check_output(command).splitlines()]
     # Only interested in dissector files.
-    files = list(filter(lambda f : isDissectorFile(f), files))
+    files = list(filter(lambda f : is_dissector_file(f), files))
     # Staged changes.
     command = ['git', 'diff', '--staged', '--name-only']
     files_staged = [f.decode('utf-8')
                     for f in subprocess.check_output(command).splitlines()]
     # Only interested in dissector files.
-    files_staged = list(filter(lambda f : isDissectorFile(f), files_staged))
+    files_staged = list(filter(lambda f : is_dissector_file(f), files_staged))
     for f in files:
         files.append(f)
     for f in files_staged: