Improving failure messages on this test

test/slow/node 0.6.21 should install 0.6.21-pre

diff --git a/test/slow/node 0.6.21 should install 0.6.21-pre b/test/slow/node 0.6.21 should install 0.6.21-pre
index 412ecfa..c579e16 100755
--- a/test/slow/node 0.6.21 should install 0.6.21-pre
+++ b/test/slow/node 0.6.21 should install 0.6.21-pre
@@ -4,7 +4,7 @@
 
 . ../../nvm.sh
 
-nvm install 0.6.21
-[ "$(node -v)" = "v0.6.21-pre" ] || die "v0.6.21-pre not installed with v0.6.21"
-[ "$(nvm current)" = "v0.6.21" ] || die "v0.6.21-pre not reported as v0.6.21"
+nvm install 0.6.21 || die 'v0.6.21 installation failed'
+[ "$(node -v)" = "v0.6.21-pre" ] || die "v0.6.21-pre not installed with v0.6.21, got $(node -v)"
+[ "$(nvm current)" = "v0.6.21" ] || die "v0.6.21-pre not reported as v0.6.21, got $(nvm current)"