Fix importing of pyparsing

[robertodr]

If an older pyparsing is available (and it usually always is), then it is imported, but it won't work with the parser generated by parselglossy. I've added a check so that if the existing pyparsing is not of major version >=3, the local copy is used instead. I will port this to parselglossy itself as well.

[codecov[bot]]

Codecov Report

Merging #420 (37295f0) into master (9a55e74) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #420   +/-   ##
=======================================
  Coverage   68.38%   68.38%           
=======================================
  Files         183      183           
  Lines       15448    15448           
=======================================
  Hits        10564    10564           
  Misses       4884     4884           

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