tests: Disallow use of util.subp except for where needed.

In many cases, cloud-init uses 'util.subp' to run a subprocess.
This is not really desirable in our unit tests as it makes the tests
dependent upon existance of those utilities.

The change here is to modify the base test case class (CiTestCase) to
raise exception any time subp is called.  Then, fix all callers.
For cases where subp is necessary or actually desired, we can use it
via
  a.) context hander CiTestCase.allow_subp(value)
  b.) class level self.allowed_subp = value

Both cases the value is a list of acceptable executable names that
will be called (essentially argv[0]).

Some cleanups in AltCloud were done as the code was being updated.

1 files changed, 43 insertions, 0 deletions

diff --git a/cloudinit/tests/helpers.py b/cloudinit/tests/helpers.py
index 9a21426e..e7e4182f 100644
--- a/cloudinit/tests/helpers.py
+++ b/cloudinit/tests/helpers.py
@@ -33,6 +33,8 @@ from cloudinit import helpers as ch
 from cloudinit.sources import DataSourceNone
 from cloudinit import util
 
+_real_subp = util.subp
+
 # Used for skipping tests
 SkipTest = unittest2.SkipTest
 skipIf = unittest2.skipIf
@@ -143,6 +145,17 @@ class CiTestCase(TestCase):
     # Subclass overrides for specific test behavior
     # Whether or not a unit test needs logfile setup
     with_logs = False
+    allowed_subp = False
+    SUBP_SHELL_TRUE = "shell=true"
+
+    @contextmanager
+    def allow_subp(self, allowed_subp):
+        orig = self.allowed_subp
+        try:
+            self.allowed_subp = allowed_subp
+            yield
+        finally:
+            self.allowed_subp = orig
 
     def setUp(self):
         super(CiTestCase, self).setUp()
@@ -155,11 +168,41 @@ class CiTestCase(TestCase):
             handler.setFormatter(formatter)
             self.old_handlers = self.logger.handlers
             self.logger.handlers = [handler]
+        if self.allowed_subp is True:
+            util.subp = _real_subp
+        else:
+            util.subp = self._fake_subp
+
+    def _fake_subp(self, *args, **kwargs):
+        if 'args' in kwargs:
+            cmd = kwargs['args']
+        else:
+            cmd = args[0]
+
+        if not isinstance(cmd, six.string_types):
+            cmd = cmd[0]
+        pass_through = False
+        if not isinstance(self.allowed_subp, (list, bool)):
+            raise TypeError("self.allowed_subp supports list or bool.")
+        if isinstance(self.allowed_subp, bool):
+            pass_through = self.allowed_subp
+        else:
+            pass_through = (
+                (cmd in self.allowed_subp) or
+                (self.SUBP_SHELL_TRUE in self.allowed_subp and
+                 kwargs.get('shell')))
+        if pass_through:
+            return _real_subp(*args, **kwargs)
+        raise Exception(
+            "called subp. set self.allowed_subp=True to allow\n subp(%s)" %
+            ', '.join([str(repr(a)) for a in args] +
+                      ["%s=%s" % (k, repr(v)) for k, v in kwargs.items()]))
 
     def tearDown(self):
         if self.with_logs:
             # Remove the handler we setup
             logging.getLogger().handlers = self.old_handlers
+        util.subp = _real_subp
         super(CiTestCase, self).tearDown()
 
     def tmp_dir(self, dir=None, cleanup=True):