diff --git a/IPython/html/fabfile.py b/IPython/html/fabfile.py
index ef6a6cb..35033c6 100644
--- a/IPython/html/fabfile.py
+++ b/IPython/html/fabfile.py
@@ -33,13 +33,17 @@ def _compile_less(source, target, minify=True, verbose=False):
ver_flag = '--verbose' if verbose is True else ''
# pin less to 1.4
- out = check_output(['lessc', '--version'])
+ try:
+ out = check_output(['lessc', '--version'])
+ except OSError as err:
+ raise ValueError("Unable to find lessc. Please install lessc >= %s and < %s " \
+ % (min_less_version, max_less_version))
out = out.decode('utf8', 'replace')
less_version = out.split()[1]
if V(less_version) < V(min_less_version):
raise ValueError("lessc too old: %s < %s" % (less_version, min_less_version))
- if V(less_version) > V(max_less_version):
- raise ValueError("lessc too new: %s > %s" % (less_version, max_less_version))
+ if V(less_version) >= V(max_less_version):
+ raise ValueError("lessc too new: %s >= %s" % (less_version, max_less_version))
with lcd(static_dir):
local('lessc {min_flag} {ver_flag} {source} {target}'.format(**locals()))