fix a number of warnings found by Starlark analyzer

lib/unittest.bzl

diff --git a/lib/unittest.bzl b/lib/unittest.bzl
index de81a4d..116bb0a 100644
--- a/lib/unittest.bzl
+++ b/lib/unittest.bzl
@@ -64,6 +64,12 @@
     """Derives the name of the given rule implementation function.
 
     This can be used for better test feedback.
+
+    Args:
+      impl: the rule implementation function
+
+    Returns:
+      The name of the given function
     """
 
     # Starlark currently stringifies a function as "<function NAME>", so we use
@@ -123,6 +129,7 @@
 _ActionInfo = provider(fields = ["actions"])
 
 def _action_retrieving_aspect_impl(target, ctx):
+    _ignore = [ctx]
     return [_ActionInfo(actions = target.actions)]
 
 _action_retrieving_aspect = aspect(
@@ -282,6 +289,9 @@
 
     Args:
       env: The test environment returned by `analysistest.begin`.
+
+    Returns:
+      A list of providers needed to automatically register the analysis test result.
     """
     return [AnalysisTestResultInfo(
         success = (len(env.failures) == 0),
@@ -296,6 +306,9 @@
 
     Args:
       env: The test environment returned by `unittest.begin`.
+
+    Returns:
+      A list of providers needed to automatically register the test result.
     """
 
     tc = env.ctx.toolchains[TOOLCHAIN_TYPE].unittest_toolchain_info
@@ -419,7 +432,6 @@
     """
     dep = _target_under_test(env)
     if AnalysisFailureInfo in dep:
-        dep_failure = dep[AnalysisFailureInfo]
         actual_errors = ""
         for cause in dep[AnalysisFailureInfo].causes.to_list():
             actual_errors += cause.message + "\n"
@@ -435,6 +447,9 @@
 
     Args:
       env: The test environment returned by `analysistest.begin`.
+
+    Returns:
+      A list of actions registered by the target under test
     """
 
     # Validate?
@@ -446,6 +461,9 @@
 
     Args:
       env: The test environment returned by `analysistest.begin`.
+
+    Returns:
+      The target under test.
     """
     result = getattr(env.ctx.attr, "target_under_test")
     if types.is_list(result):

rules/analysis_test.bzl

diff --git a/rules/analysis_test.bzl b/rules/analysis_test.bzl
index 0ac404b..a43ef90 100644
--- a/rules/analysis_test.bzl
+++ b/rules/analysis_test.bzl
@@ -16,6 +16,7 @@
 
 def _analysis_test_impl(ctx):
     """Implementation function for analysis_test. """
+    _ignore = [ctx]
     return [AnalysisTestResultInfo(
         success = True,
         message = "All targets succeeded analysis",

tests/unittest_tests.bzl

diff --git a/tests/unittest_tests.bzl b/tests/unittest_tests.bzl
index 20fd890..01ea4de 100644
--- a/tests/unittest_tests.bzl
+++ b/tests/unittest_tests.bzl
@@ -69,6 +69,7 @@
     return analysistest.end(env)
 
 def _failure_testing_fake_rule(ctx):
+    ignore = [ctx]
     fail("This rule should never work")
 
 failure_testing_fake_rule = rule(
@@ -92,6 +93,7 @@
     return analysistest.end(env)
 
 def _fail_unexpected_passing_fake_rule(ctx):
+    _ignore = [ctx]
     return []
 
 fail_unexpected_passing_fake_rule = rule(
@@ -168,7 +170,8 @@
 
     Not all tests are included. Some unittest.bzl tests verify a test fails
     when assertions are not met. Such tests must be run in an e2e shell test.
-    This suite only includes tests which verify success tests."""
+    This suite only includes tests which verify success tests.
+    """
     unittest.suite(
         "unittest_tests",
         basic_passing_test,