Log a helpful message if a user script does not include shebang.

A patch to allow scripts missing a #! to run by using shell=True was
proposed but rejected. Instead we emit a log message to help the user
understand what went wrong.

2 files changed, 24 insertions, 9 deletions

diff --git a/cloudinit/util.py b/cloudinit/util.py
index ce2c6034..609e94c8 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -12,7 +12,6 @@ import contextlib
 import copy as obj_copy
 import ctypes
 import email
-import errno
 import glob
 import grp
 import gzip
@@ -34,6 +33,8 @@ import sys
 import tempfile
 import time
 
+from errno import ENOENT, ENOEXEC
+
 from base64 import b64decode, b64encode
 from six.moves.urllib import parse as urlparse
 
@@ -239,7 +240,10 @@ class ProcessExecutionError(IOError):
             self.cmd = cmd
 
         if not description:
-            self.description = 'Unexpected error while running command.'
+            if not exit_code and errno == ENOEXEC:
+                self.description = 'Exec format error. Missing #! in script?'
+            else:
+                self.description = 'Unexpected error while running command.'
         else:
             self.description = description
 
@@ -433,7 +437,7 @@ def read_conf(fname):
     try:
         return load_yaml(load_file(fname), default={})
     except IOError as e:
-        if e.errno == errno.ENOENT:
+        if e.errno == ENOENT:
             return {}
         else:
             raise
@@ -901,7 +905,7 @@ def read_file_or_url(url, timeout=5, retries=10,
             contents = load_file(file_path, decode=False)
         except IOError as e:
             code = e.errno
-            if e.errno == errno.ENOENT:
+            if e.errno == ENOENT:
                 code = url_helper.NOT_FOUND
             raise url_helper.UrlError(cause=e, code=code, headers=None,
                                       url=url)
@@ -1247,7 +1251,7 @@ def find_devs_with(criteria=None, oformat='device',
     try:
         (out, _err) = subp(cmd, rcs=[0, 2])
     except ProcessExecutionError as e:
-        if e.errno == errno.ENOENT:
+        if e.errno == ENOENT:
             # blkid not found...
             out = ""
         else:
@@ -1285,7 +1289,7 @@ def load_file(fname, read_cb=None, quiet=False, decode=True):
     except IOError as e:
         if not quiet:
             raise
-        if e.errno != errno.ENOENT:
+        if e.errno != ENOENT:
             raise
     contents = ofh.getvalue()
     LOG.debug("Read %s bytes from %s", len(contents), fname)
@@ -1653,7 +1657,7 @@ def del_file(path):
     try:
         os.unlink(path)
     except OSError as e:
-        if e.errno != errno.ENOENT:
+        if e.errno != ENOENT:
             raise e
 
 
@@ -2281,7 +2285,7 @@ def pathprefix2dict(base, required=None, optional=None, delim=os.path.sep):
         try:
             ret[f] = load_file(base + delim + f, quiet=False, decode=False)
         except IOError as e:
-            if e.errno != errno.ENOENT:
+            if e.errno != ENOENT:
                 raise
             if f in required:
                 missing.append(f)
diff --git a/tests/unittests/test_util.py b/tests/unittests/test_util.py
index f38a664c..5f11c88f 100644
--- a/tests/unittests/test_util.py
+++ b/tests/unittests/test_util.py
@@ -568,7 +568,8 @@ class TestReadSeeded(helpers.TestCase):
         self.assertEqual(found_ud, ud)
 
 
-class TestSubp(helpers.TestCase):
+class TestSubp(helpers.CiTestCase):
+    with_logs = True
 
     stdin2err = [BASH, '-c', 'cat >&2']
     stdin2out = ['cat']
@@ -650,6 +651,16 @@ class TestSubp(helpers.TestCase):
         self.assertEqual(
             ['FOO=BAR', 'HOME=/myhome', 'K1=V1', 'K2=V2'], out.splitlines())
 
+    def test_subp_warn_missing_shebang(self):
+        """Warn on no #! in script"""
+        noshebang = self.tmp_path('noshebang')
+        util.write_file(noshebang, 'true\n')
+
+        os.chmod(noshebang, os.stat(noshebang).st_mode | stat.S_IEXEC)
+        self.assertRaisesRegexp(util.ProcessExecutionError,
+                                'Missing #! in script\?',
+                                util.subp, (noshebang,))
+
     def test_returns_none_if_no_capture(self):
         (out, err) = util.subp(self.stdin2out, data=b'', capture=False)
         self.assertIsNone(err)