  The quotient $L/A[-1]$ of a pair $A\hookrightarrow L$ of Lie algebroids is a
Lie algebra object in the derived category $D^b(\mathscr{A})$ of the category
$\mathscr{A}$ of left $\mathcal{U}(A)$-modules, the Atiyah class $\alpha_{L/A}$
being its Lie bracket. In this note, we describe the universal enveloping
algebra of the Lie algebra object $L/A[-1]$ and we prove that it is a Hopf
algebra object in $D^b(\mathscr{A})$.
