[#1877] hammer: hardcoded sphinx version for centos

diff --git a/hammer.py b/hammer.py
index 7d350807cec9ae4b89bcf70c932840a771d2e5c2..64697c735404fc8b5838fd1eadc0c01c15eb4131 100755 (executable)
--- a/hammer.py
+++ b/hammer.py
@@ -1303,7 +1303,7 @@ def prepare_system_local(features, check_times):
         if 'docs' in features:
             execute('virtualenv-3 ~/venv',
                     env=env, timeout=60, check_times=check_times)
-            execute('~/venv/bin/pip install sphinx sphinx-rtd-theme',
+            execute('~/venv/bin/pip install sphinx==3.5.4 sphinx-rtd-theme==0.5.2',
                     env=env, timeout=120, check_times=check_times)
 
         if 'unittest' in features: