This is a combination of upstream's fe2d8334 and 03abad.  See
https://bugs.gentoo.org/show_bug.cgi?id=574610.

diff -Naur fdupes-1.51.orig/fdupes.c fdupes-1.51/fdupes.c
--- fdupes-1.51.orig/fdupes.c	2013-04-20 14:02:18.000000000 -0400
+++ fdupes-1.51/fdupes.c	2016-02-29 02:45:36.360804360 -0500
@@ -1164,7 +1164,12 @@
     }
     else
     {
-      stdin = freopen("/dev/tty", "r", stdin);
+      if (freopen("/dev/tty", "r", stdin) == 0)
+      {
+        errormsg("could not open terminal for input\n");
+        exit(1);
+      }
+
       deletefiles(files, 1, stdin);
     }
   }