RF: get DEBUG_PRINT from environment
RF: get DEBUG_PRINT from environment

From Yarik's suggestion.

alexis-roche/nipy,bthirion/nipy,nipy/nireg,bthirion/nipy,alexis-roche/nipy,alexis-roche/register,nipy/nipy-labs,bthirion/nipy,bthirion/nipy,alexis-roche/register,alexis-roche/nipy,arokem/nipy,alexis-roche/nireg,alexis-roche/register,nipy/nipy-labs,arokem/nipy,nipy/nireg,alexis-roche/nipy,arokem/nipy,alexis-roche/nireg,alexis-roche/niseg,arokem/nipy,alexis-roche/niseg