PR: Force reading of path stored in Spyder configuration folder as utf-8

[rhkarls]

Description of Changes

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)

• Included a screenshot or animation (if affecting the UI, see Licecap)

See issue #15692 for description.
The path file in the spyder configuration directory, which holds the user provided paths added with the PYTHONPATH manager is not read with correct encoding, and thus not allowing for unicode characters in the paths (e.g. 'ö'). The current read functionality is handled by encoding.readlines(), with subsequent calls to encoding.read(), encoding.decode(), encoding.get_coding() which finally calls chardet.UniversalDetector(). chardet returns (at least sometimes) the wrong encoding as per issue #15692.

Other fixes were considered

• write BOM to the path file to make sure chardet detects utf-8. Using BOM with utf-8 appears, however, to be generally discourages (https://stackoverflow.com/questions/2223882/whats-the-difference-between-utf-8-and-utf-8-without-bom/2223926#2223926)
• rewrite functions in encoding.py to allow for defining the encoding when reading a file (note that read/readlines has a kw encoding, but this is ignored and not used). However, would require more changes, and considered unnecessary complicated and more likely to break other parts of the code due to the extensive use of the read() function in utils/encoding.py

The proposed and simple solution in this PR simply reads the file with encoding set to utf-8. The path file is written by encoding.write() and encoding.encode() should encode the text using utf-8.

Issue(s) Resolved

Fixes #15692

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: Reinert Huseby Karlsen

[ccordoba12]

@rhkarls, thanks a lot for your contribution! Very clean and simple solution to the problem you reported.