Escape filename characters instead of dropping them.

[bittaurus]

I noticed you drop filesystem reserved characters from the filename.

Consider that this can cause other problems:

Resulting filename can be empty if all characters are invalid.
Resulting filename can be "special" dependant on the OS, like ".", "..", "CON" in windows, etc.

In linux, the only invalid printable character is '/'.

Also, dropping / will remove things like date delimination in the format:

"11/1/1999" and "1/11/1999" become equal and a collision.

Windows has an infinite number of invalid filenames. For example one composed of only dots and spaces is invalid.

As a baseline for linux, would the best practice be to escape problematic characters and convert / to another character?

[bittaurus]

the following mod to scdl.py replaces invalid characters with '_' instead of dropping them:

in get_filename():

filename = ''.join([(c if c not in invalid_chars else "_") for c in filename])