Replace deprecated library function os.popen() with subprocess

os.popen() is deprecated since version 2.6. Resolved with use of
subprocess module.

Change-Id: Iea9c0501f46c57d809217912fb0f40eb2bc4f111
Closes-Bug: #1529836

api-guide/source/conf.py

@@ -19,7 +19,7 @@
 # serve to show the default.
 
 # import sys
-import os
+import subprocess
 
 import openstackdocstheme
 
@@ -81,10 +81,15 @@ release = '2.1.0'
 #   bug_project: Launchpad project to file bugs against.
 # These variables are passed to the logabug code via html_context.
 giturl = u'http://git.openstack.org/cgit/openstack/nova/tree/api-guide/source'
-git_cmd = "/usr/bin/git log | head -n1 | cut -f2 -d' '"
+git_cmd = ["/usr/bin/git", "rev-parse", "HEAD"]
-gitsha = os.popen(git_cmd).read().strip('\n')
+gitsha = subprocess.Popen(
+    git_cmd, stdout=subprocess.PIPE).communicate()[0]
+
+
 # source tree
-pwd = os.popen("pwd").read().strip('\n')
+pwd = subprocess.Popen(
+    "pwd", stdout=subprocess.PIPE).communicate()[0].strip('\n')
+
 # html_context allows us to pass arbitrary values into the html template
 html_context = {"pwd": pwd,
                 "gitsha": gitsha,

doc/source/conf.py

@@ -12,6 +12,7 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
+import subprocess
 import sys
 import os
 
@@ -194,8 +195,10 @@ html_static_path = ['_static']
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
 #html_last_updated_fmt = '%b %d, %Y'
-git_cmd = "git log --pretty=format:'%ad, commit %h' --date=local -n1"
+git_cmd = ["git", "log", "--pretty=format:'%ad, commit %h'", "--date=local",
-html_last_updated_fmt = os.popen(git_cmd).read()
+    "-n1"]
+html_last_updated_fmt = subprocess.Popen(
+    git_cmd, stdout=subprocess.PIPE).communicate()[0]
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.