Merge "Fix doc build if git is absent"

doc/source/conf.py

@@ -24,6 +24,7 @@
 # serve to show the default.
 
 import subprocess
+import warnings
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
@@ -158,8 +159,13 @@ html_static_path = ['_static']
 # html_last_updated_fmt = '%b %d, %Y'
 git_cmd = ["git", "log", "--pretty=format:'%ad, commit %h'", "--date=local",
            "-n1"]
-html_last_updated_fmt = subprocess.Popen(
-    git_cmd, stdout=subprocess.PIPE).communicate()[0]
+try:
+    html_last_updated_fmt = subprocess.Popen(
+        git_cmd, stdout=subprocess.PIPE).communicate()[0]
+except Exception:
+    warnings.warn('Cannot get last updated time from git repository. '
+                  'Not setting "html_last_updated_fmt".')
+
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.