Update lockable_trait.rst for blocking lock#8076

Merged

xabbuh merged 2 commits intosymfony:3.2from

lpussacq:patch-1

Jul 7, 2017

Commits on Jun 22, 2017

Update lockable_trait.rst
lpussacq
authored

Commits on Jul 6, 2017

Use "null" so the lock is named automatically
javiereguiluz
authored