speedup for docbuild using joblib
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Merge pull request #2620 from jaquesgrobler/master

ENH: speedup for docbuild using joblib
fix broken link for stable version from dev version
FIX: unintended assignment to ValueError
STY: tuple for Gael
ENH: refactor warnings 1
ENH: add assert_warn_message
ENH: revem tests_metrics.py
ENH: more of this
ENH: final fix: clear all regisitries
FIX: PPCA related warnings
ENH: context manager + decorator
FIX: doc example
ENH: address discussion
ENH: address discussion
rebase
cosmits
FIX

FIX typo
FIX typo 2