Hacking: check for deprecated os.popen()

Add hacking check for deprecated library function os.popen().
This hacking prevents new os.popen() in the code.

Closes-Bug: 1529836

Change-Id: I09ad101861b790d2f9bec45757b8c921e68b696e

HACKING.rst

@@ -58,6 +58,7 @@ Nova Specific Commandments
 - [N345] Python 3: do not use dict.iterkeys.
 - [N346] Python 3: do not use dict.itervalues.
 - [N347] Provide enough help text for config options
+- [N348] Deprecated library function os.popen()
 
 Creating Unit Tests
 -------------------

nova/hacking/checks.py

@@ -683,6 +683,20 @@ def cfg_help_with_enough_text(logical_line, tokens):
         yield(0, msg)
 
 
+def no_os_popen(logical_line):
+    """Disallow 'os.popen('
+
+    Deprecated library function os.popen() Replace it using subprocess
+    https://bugs.launchpad.net/tempest/+bug/1529836
+
+    N348
+    """
+
+    if 'os.popen(' in logical_line:
+        yield(0, 'N348 Deprecated library function os.popen(). '
+                 'Replace it using subprocess module. ')
+
+
 def factory(register):
     register(import_no_db_in_virt)
     register(no_db_session_in_public_api)
@@ -717,3 +731,4 @@ def factory(register):
     register(check_python3_no_iterkeys)
     register(check_python3_no_itervalues)
     register(cfg_help_with_enough_text)
+    register(no_os_popen)

nova/tests/unit/test_hacking.py

@@ -732,3 +732,21 @@ class HackingTestCase(test.NoDBTestCase):
         \"\"\")
         """
         self._assert_has_no_errors(code9, checks.cfg_help_with_enough_text)
+
+    def test_no_os_popen(self):
+        code = """
+               import os
+
+               foobar_cmd = "foobar -get -beer"
+               answer = os.popen(foobar_cmd).read()
+
+               if answer == nok":
+                   try:
+                       os.popen(os.popen('foobar -beer -please')).read()
+
+                   except ValueError:
+                       go_home()
+               """
+        errors = [(4, 0, 'N348'), (8, 8, 'N348')]
+        self._assert_has_errors(code, checks.no_os_popen,
+                                expected_errors=errors)