fix the documentation and the error message of modpath_from_file

[temyurchenko]

The doc should clarify that the search will always include sys.path.

The error message should reflect the actual paths used for checking.

Type of Changes

	Type
✓	📜 Docs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.98%. Comparing base (a389ef7) to head (c551ff9).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2532      +/-   ##
==========================================
- Coverage   92.98%   92.98%   -0.01%     
==========================================
  Files          93       93              
  Lines       11049    11048       -1     
==========================================
- Hits        10274    10273       -1     
  Misses        775      775              

Flag	Coverage Δ
linux	92.85% <ø> (-0.01%)	⬇️
pypy	92.98% <ø> (-0.01%)	⬇️
windows	92.96% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
astroid/modutils.py	89.47% <ø> (ø)

... and 1 file with indirect coverage changes

[Pierre-Sassoulas]

Thank you 👌