I also have pstoedit installed as a consequence of the MacPorts installation of Octave and I had similar problems today with building pstoedit 3.70_3 (when doing a "sudo port upgrade outdated") and found success with temporarily renaming /usr/local to /usr/local-temp
This temporary renaming of /usr/local can be seen as a suggestion in various places such as https://trac.macports.org/wiki/FAQ#usrlocal
What worked for me was:
sudo port clean --all pstoedit sudo mv /usr/local /usr/local-temp sudo port install --unrequested pstoedit sudo mv /usr/local-temp /usr/local
The --unrequested flag was used since pstoedit is not something I need by itself, but only as dependant for some of my requested ports (namely Octave).
Probably we should report somewhere that this was necessary.
It is possible that the same effect could have been accomplished by using the "-t" flag as referenced in the FAQ linked above, but I did not try that.
sudo port -t install --unrequested pstoedit