This equation array
\begin{eqnarray}
|z-z_i| <\delta_i/2,\\
|w-z_i| &=& |w-z+z-z_i| \nonumber\\
&\leq& |w-z| + |z-z_i| \nonumber \\
& <& \delta + \delta_i/2 \nonumber\\
& \leq& \delta_i/2 + \delta_i/2 \nonumber \\
&<& \delta_i.
\end{eqnarray}is transformed to
\begin{align}I_n &=& \left|\int_{\partial \Delta_n} f(z)\,\mbox{d} z\right| \\
&= &
\left|\int_{\partial \Delta_n} \left(f(z) - f(z_0) -
(z-z_0)f'(z_0)\right)\,\mbox{d} z\right| \\
&\leqslant & \len(\partial \Delta_n)\varepsilon\sup_{z \in \partial \Delta_n}|z-z_0|.\end{align}but this is not the way of writing an align, since this would make the equations to be aligned on the right side of the page. The correct way of writing an align is:
\begin{align}I_n &= \left|\int_{\partial \Delta_n} f(z)\,\mbox{d} z\right| \\
&=
\left|\int_{\partial \Delta_n} \left(f(z) - f(z_0) -
(z-z_0)f'(z_0)\right)\,\mbox{d} z\right| \\
&\leqslant \operatorname{length}(\partial \Delta_n)\varepsilon\sup_{z \in \partial \Delta_n}|z-z_0|.\end{align}The solution is not that easy, it is not trivial to chose which & remove for having the correct the alignment.
To complete this task handle the eqnarray block type in MediaWikiRenderer.py separately from the align block.
You have to modify the math content checking that between every \\ there's only one &.
Be CAREFUL: you have to check that is & NOT \&
Please pull request your work.