- document post-fetch networking note

PR:		207416 (based on)
Submitted by:	482254ac@razorfever.net
Approved by:	bcr (mentor)
Differential Revision:	https://reviews.freebsd.org/D5405

en_US.ISO8859-1/books/porters-handbook/quick-porting/chapter.xml

@@ -258,6 +258,13 @@ lib/X11/oneko/mouse.xpm</programlisting>
 	  verifies that the deinstall script works correctly.</para>
       </listitem>
 
+      <listitem>
+	<para>The port does not access network resources after the
+	  <buildtarget>fetch</buildtarget> target.  This is important
+	  for package builders, such as <package
+	    role="port">ports-mgmt/poudriere</package>.</para>
+      </listitem>
+
       <listitem>
 	<para>Make sure that <command>make package</command> can be
 	  run as a normal user (that is, not as