[Doitsu]

@CalibUser: I tested the plugin with a UTF-8 text file and it didn't decode it correctly.
Since Sigil comes with bs4, I'd recommend using soup.original_encoding to detect the original encoding.

For example:

from sigil_bs4 import BeautifulSoup

def run(bk):
    # more code...
    with open(fHandle.name, "rb") as binary_file:
        data = binary_file.read()
        soup = BeautifulSoup(data) 
        print(soup.original_encoding)
        return -1
        # more code...

The above code correctly identified my UTF-8 test file. Of course, if you use bs4 as a filter, you might as well use str(soup) to convert an input file with unknown encoding to UTF-8.