Fix docs failures caused by latest eventlet

Closes-bug: #1674687

Change-Id: I9c44f84b1eb4f25a2c87612b444d22f12e6f22ce

doc/source/conf.py

@@ -22,13 +22,19 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
+import eventlet
 import os
-import subprocess
 import sys
 import warnings
 
 from cinder import objects
 
+# NOTE(dims): monkey patch subprocess to prevent failures in latest eventlet
+# See https://github.com/eventlet/eventlet/issues/398
+try:
+    eventlet.monkey_patch(subprocess=True)
+except TypeError:
+    pass
 
 # NOTE(geguileo): Sphinx will fail to generate the documentation if we are
 # using decorators from any OVO in cinder.objects, because the OVOs are only
@@ -198,6 +204,7 @@ html_static_path = ['_static']
 git_cmd = ["git", "log", "--pretty=format:%ad, commit %h", "--date=local",
            "-n1"]
 try:
+    import subprocess
     html_last_updated_fmt = subprocess.check_output(git_cmd).decode('utf-8')
 except Exception:
     warnings.warn('Cannot get last updated time from git repository. '