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, 17 insertions, 12 deletions

diff --git a/cloudinit/sources/DataSourceSmartOS.py b/cloudinit/sources/DataSourceSmartOS.py
index ad8cfb9c..593ac91a 100644
--- a/cloudinit/sources/DataSourceSmartOS.py
+++ b/cloudinit/sources/DataSourceSmartOS.py
@@ -683,6 +683,18 @@ def jmc_client_factory(
     raise ValueError("Unknown value for smartos_type: %s" % smartos_type)
 
 
+def identify_file(content_f):
+    cmd = ["file", "--brief", "--mime-type", content_f]
+    f_type = None
+    try:
+        (f_type, _err) = util.subp(cmd)
+        LOG.debug("script %s mime type is %s", content_f, f_type)
+    except util.ProcessExecutionError as e:
+        util.logexc(
+            LOG, ("Failed to identify script type for %s" % content_f, e))
+    return None if f_type is None else f_type.strip()
+
+
 def write_boot_content(content, content_f, link=None, shebang=False,
                        mode=0o400):
     """
@@ -715,18 +727,11 @@ def write_boot_content(content, content_f, link=None, shebang=False,
     util.write_file(content_f, content, mode=mode)
 
     if shebang and not content.startswith("#!"):
-        try:
-            cmd = ["file", "--brief", "--mime-type", content_f]
-            (f_type, _err) = util.subp(cmd)
-            LOG.debug("script %s mime type is %s", content_f, f_type)
-            if f_type.strip() == "text/plain":
-                new_content = "\n".join(["#!/bin/bash", content])
-                util.write_file(content_f, new_content, mode=mode)
-                LOG.debug("added shebang to file %s", content_f)
-
-        except Exception as e:
-            util.logexc(LOG, ("Failed to identify script type for %s" %
-                              content_f, e))
+        f_type = identify_file(content_f)
+        if f_type == "text/plain":
+            util.write_file(
+                content_f, "\n".join(["#!/bin/bash", content]), mode=mode)
+            LOG.debug("added shebang to file %s", content_f)
 
     if link:
         try: