tests/fate-run.sh: Cat .err file in case of error with V>0

This may make fate failures where only the console output is available
easier to analyze

Suggested-by: Andreas Cadhalpun
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 00d3bb1a07)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

tests/fate-run.sh

@@ -248,6 +248,7 @@ if test $err = 0; then
     rm -f $outfile $errfile $cmpfile $cleanfiles
 elif test $gen = "no"; then
     echo "Test $test failed. Look at $errfile for details."
+    test "${V:-0}" -gt 0 && cat $errfile
 else
     echo "Updating reference failed, possibly no output file was generated."
 fi