Merge branch 'bc/portable'

* bc/portable: Remove python 2.5'isms Makefile: add PYTHON_PATH to GIT-BUILD-OPTIONS t/aggregate-results: accomodate systems with small max argument list length t/t7006: ignore return status of shell's unset builtin t/t5150: remove space from sed script git-request-pull.sh: remove -e switch to shell interpreter which breaks ksh t/t5800: skip if python version is older than 2.5