Use urllib2 instead of requests in tempest generate plugin list

While using generate-tempest-plugins-list.py in tempest-plugin-sanity
CI jobs fails to run as it requires requests module to parse the git
url and is not install by default in CI job. If we are going to
install requests we need to use sudo for that which is not a
good idea, so it is better to move the script to urllib2.

Change-Id: Ifed51c67c03f993a4833413826ac15104db152fc

tools/generate-tempest-plugins-list.py

@@ -26,7 +26,12 @@
 import json
 import re
 
-import requests
+try:
+    # For Python 3.0 and later
+    import urllib
+except ImportError:
+    # Fall back to Python 2's urllib2
+    import urllib2 as urllib
 
 url = 'https://review.openstack.org/projects/'
 
@@ -49,21 +54,23 @@ def is_in_openstack_namespace(proj):
 
 
 def has_tempest_plugin(proj):
-    if proj.startswith('openstack/deb-'):
-        return False
-    r = requests.get(
-        "https://git.openstack.org/cgit/%s/plain/setup.cfg" % proj)
+    try:
+        r = urllib.urlopen("https://git.openstack.org/cgit/%s/plain/setup.cfg"
+                           % proj)
+    except urllib.HTTPError as err:
+        if err.code == 404:
+            return False
     p = re.compile('^tempest\.test_plugins', re.M)
-    if p.findall(r.text):
+    if p.findall(r.read()):
         return True
     else:
         False
 
-r = requests.get(url)
+r = urllib.urlopen(url)
 # Gerrit prepends 4 garbage octets to the JSON, in order to counter
 # cross-site scripting attacks.  Therefore we must discard it so the
 # json library won't choke.
-projects = sorted(filter(is_in_openstack_namespace, json.loads(r.text[4:])))
+projects = sorted(filter(is_in_openstack_namespace, json.loads(r.read()[4:])))
 
 found_plugins = filter(has_tempest_plugin, projects)