The problem is that gnu have moved the file so you do not get the source of automake when homebrew downloads it.
If you download the file ttphttp://ftpmirror.gnu.org/automake/automake-1.14.tar.gz
you get
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>302 Found</title>
</head><body>
<h1>Found</h1>
<p>The document has moved <a href="http://ftp.heanet.ie/mirrors/gnu/automake/automake-1.14.tar.gz">here</a>.</p>
<hr>
<address>Apache/2.2.16 (Debian) Server at ftpmirror.gnu.org Port 80</address>
</body></html>