subprocess Runtime warning: RuntimeWarning: line buffering (buffering=1) isn't supported in binary mode, the default buffer size will be used

[DarkTrick]

Describe the bug
Running "Run selected" on a top-level item, causes "Test output ended unexpectedly" in cricket with the following message in the console.

/usr/lib/python3.8/subprocess.py:844: RuntimeWarning: line buffering (buffering=1) isn't supported in binary mode, the default buffer size will be used
  self.stdout = io.open(c2pread, 'rb', bufsize)
/usr/lib/python3.8/subprocess.py:849: RuntimeWarning: line buffering (buffering=1) isn't supported in binary mode, the default buffer size will be used
  self.stderr = io.open(errread, 'rb', bufsize)

(This does not happen, when I "Run all")

To Reproduce

1. Create a test project
2. Open cricket
3. Select test "folder"
4. Click "Run selected"
5.  
   • EXPECTED: Tests run and their output is shown.
   • ACTUAL: Test results are not shown (I can't tell if tests were run)

Misc

• Everything works fine when I use "Run all"
• Everything works fine, when I "Run selected" on a "python file"
• Behaviour started after upgrading packages via pip
• I tried reinstalling cricket: no change

Screenshots

Environment:

• Operating System: XUbuntu 20.10
• Python version: 3.8.6