hacking: check for deprecated os.open()

Add hacking check for deprecated library function os.popen().
This bug was reported https://bugs.launchpad.net/tempest/+bug/1529836
and this hacking prevents new os.popen() in the code.

Change-Id: I124b9f86ffc6eba268c99ad9834686f55fd857c3

HACKING.rst

@@ -10,6 +10,8 @@ Nova-PowerVM Specific Commandments
 - Follow the Nova HACKING.rst
 
 - [P301] LOG.warn() is not allowed. Use LOG.warning()
+- [P302] Deprecated library function os.popen()
+
 
 Creating Unit Tests
 -------------------

nova_powervm/hacking/checks.py

@@ -25,6 +25,21 @@ def no_log_warn(logical_line, filename):
         yield(0, 'P301 Use LOG.warning() rather than LOG.warn()')
 
 
+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
+
+    P302
+    """
+
+    if 'os.popen(' in logical_line:
+        yield(0, 'P302 Deprecated library function os.popen(). '
+                 'Replace it using subprocess module. ')
+
+
 def factory(register):
     register(no_log_warn)
+    register(no_os_popen)
     checks.factory(register)