Fully read's processBodyError argument needs to take an exception

Fixes #1636.

fetch.bs

@@ -1510,7 +1510,8 @@ must be an algorithm accepting an exception.
 <var>processBody</var>, an algorithm <var>processBodyError</var>, and an optional null,
 <a for=/>parallel queue</a>, or <a for=/>global object</a> <var>taskDestination</var> (default
 null), run these steps. <var>processBody</var> must be an algorithm accepting a
-<a for=/>byte sequence</a>. <var>processBodyError</var> must be an algorithm accepting no arguments.
+<a for=/>byte sequence</a>. <var>processBodyError</var> must be an algorithm optionally accepting an
+<a for=/>exception</a>.
 
 <ol>
  <li><p>If <var>taskDestination</var> is null, then set <var>taskDestination</var> to the result of
@@ -1520,8 +1521,9 @@ null), run these steps. <var>processBody</var> must be an algorithm accepting a
  <a>queue a fetch task</a> to run <var>processBody</var> given <var>bytes</var>, with
  <var>taskDestination</var>.
 
- <li><p>Let <var>errorSteps</var> be to <a>queue a fetch task</a> to run
- <var>processBodyError</var>, with <var>taskDestination</var>.
+ <li><p>Let <var>errorSteps</var> optionally given an <a for=/>exception</a> <var>exception</var> be
+ to <a>queue a fetch task</a> to run <var>processBodyError</var> given <var>exception</var>, with
+ <var>taskDestination</var>.
 
  <li><p>Let <var>reader</var> be the result of <a for=ReadableStream>getting a reader</a> for
  <var>body</var>'s <a for=body>stream</a>. If that threw an exception, then run
@@ -8988,6 +8990,7 @@ Rondinelly,
 Rory Hewitt,
 Ross A. Baker,
 Ryan Sleevi,
+Sam Atkins,
 Samy Kamkar,
 Sébastien Cevey,
 Sendil Kumar N,