Add conditions to retry HTTPie install

[nntrn]

Add conditions for installing older versions of httpie if a failure occurs due to multidict dependency related issues

Attempt 1:

# install without multidict compilation:  
[[ -z $(pip show httpie 2>/dev/null) ]] &&
  MULTIDICT_NO_EXTENSIONS=1 python -m pip install --no-cache-dir httpie

Attempt 2:

# install older version without multidict dependency
[[ -z $(pip show httpie 2>/dev/null) ]] && python -m pip install httpie==2.6.0