Improve error message

Author: Vasileios Karakasis

bootstrap.sh

@@ -61,8 +61,8 @@ done
 # We need to exit with a zero code if the Python version is the correct
 # one, so we invert the comparison
 
-if $python -c 'import sys;sys.exit(sys.version_info[:2] >= (3, 6))'; then
-    echo -e "ReFrame requires Python >= 3.6"
+if $python -c 'import sys; sys.exit(sys.version_info[:2] >= (3, 6))'; then
+    echo -e "ReFrame requires Python >= 3.6 (found $($python -V 2>&1))"
     exit 1
 fi