Fix infinite loop issue

Running bandit using relative paths inside a subdirectory when the current
directory contains __init__.py causes bandit to be stuck in an infinite
loop.

Co-Authored-By: Calvin Li
Closes-Bug: #1743042
Change-Id: I247108c1365847134ee561073ea0eb43c57b54cc

bandit/core/utils.py

@@ -151,7 +151,7 @@ def get_module_qualname_from_path(path):
                                 ' Missing path or file name' % (path))
 
     qname = [os.path.splitext(tail)[0]]
-    while head not in ['/', '.']:
+    while head not in ['/', '.', '']:
         if os.path.isfile(os.path.join(head, '__init__.py')):
             (head, tail) = os.path.split(head)
             qname.insert(0, tail)

examples/init-py-test/subdirectory-okay.py

@@ -0,0 +1,3 @@
+# A sample test file in a subdirectory and its parents both containing
+# an __init__.py file outlined in bug/1743042.
+print('hopefully no vulnerabilities here')

setup.cfg

@@ -121,6 +121,8 @@ source-dir = doc/source
 
 [pbr]
 autodoc_tree_index_modules = True
+autodoc_tree_excludes =
+  examples*
 
 [bdist_wheel]
 universal = 1

tests/functional/test_functional.py

@@ -285,6 +285,14 @@ class FunctionalTests(testtools.TestCase):
         }
         self.check_example('okay.py', expect)
 
+    def test_subdirectory_okay(self):
+        '''Test a vulnerability-free file under a subdirectory.'''
+        expect = {
+            'SEVERITY': {'UNDEFINED': 0, 'LOW': 0, 'MEDIUM': 0, 'HIGH': 0},
+            'CONFIDENCE': {'UNDEFINED': 0, 'LOW': 0, 'MEDIUM': 0, 'HIGH': 0}
+        }
+        self.check_example('init-py-test/subdirectory-okay.py', expect)
+
     def test_os_chmod(self):
         '''Test setting file permissions.'''
         filename = 'os-chmod-{}.py'