Fix nosec for nested dicts

Before this commit nosec was searched from the begnning
of the expression's context, which may be broader than
the exact piece of code that a developer wants to skip.
This caused, that for the below example:

1. example = {
2.     'S3_CONFIG_PARAMS': dict(  # nosec B106
3.         ...
4.     ),
5.     'LOCALFS_BASEDIR': '/var/tmp/herp',  # nosec B108
6. }

for line 5, nosec from line 2 was returned. Thus `nosec B108` was ignored.

This commit changes the algorithm that search for nosec for an expression
and nosec from the exact line of the expression is preferred.

Resolves: PyCQA#1003

bandit/core/utils.py

@@ -373,8 +373,8 @@ def check_ast_node(name):
 
 
 def get_nosec(nosec_lines, context):
-    for lineno in context["linerange"]:
-        nosec = nosec_lines.get(lineno, None)
+    for lineno in [context["lineno"], *context["linerange"]]:
+        nosec = nosec_lines.get(lineno)
         if nosec is not None:
             return nosec
     return None

examples/nosec.py

@@ -13,3 +13,14 @@
 subprocess.Popen('/bin/ls *', shell=True) # type: ... # noqa: E501 ; pylint: disable=line-too-long # nosec
 subprocess.Popen('#nosec', shell=True) # nosec B607, B101
 subprocess.Popen('#nosec', shell=True) # nosec B602, subprocess_popen_with_shell_equals_true
+# check that nosec in nested dict does not cause "higher" annotations to be ignored
+# reproduction of https://github.com/PyCQA/bandit/issues/1003
+example = {
+    'S3_CONFIG_PARAMS': dict(  # nosec B106
+        aws_access_key_id='key_goes_here',
+        aws_secret_access_key='secret_goes_here',
+        endpoint_url='s3.amazonaws.com',
+    ),
+    'LOCALFS_BASEDIR': '/var/tmp/herp',  # nosec B108
+    'ALPINE_APORTS_DIR': '/tmp/derp',  # nosec B108
+}