labm8/py/test: Remove PYTEST_ARGS module variable.

Instead of reading a PYTEST_ARGS attribute on test modules, use bazel
to pass a --pytest_args argument, e.g.

    py_test(
        name = "foo_test",
	srcs = ["foo_test.py"],
	args = ["--pytest_args=--my_arg"],
	deps = [
	     "//labm8/py:test",
	],
    )

Signed-off-by: format 2020.01.16 <github.com/ChrisCummins/format>

deeplearning/ml4pl/graphs/labelled/dataflow/BUILD

@@ -55,6 +55,7 @@ py_test(
     size = "enormous",
     timeout = "eternal",
     srcs = ["annotators_benchmark_test.py"],
+    args = ["--pytest_args=--benchmark-warmup-iterations=2"],
     deps = [
         ":annotate",
         ":data_flow_graphs",

labm8/py/test.py

@@ -263,11 +263,6 @@ def RunPytestOnFileOrDie(file_path: str, capture_output: bool = None):
   # Add the --pytest_args requested by the user.
   pytest_args += FLAGS.pytest_args
 
-  # Allow the user to add a PYTEST_ARGS = ['--foo'] list of additional
-  # arguments.
-  if hasattr(test_module, "PYTEST_ARGS"):
-    pytest_args += test_module.PYTEST_ARGS
-
   with CoverageContext(test_module, file_path, pytest_args) as pytest_args:
     app.Log(1, "Running pytest with arguments: %s", pytest_args)
     ret = pytest.main(pytest_args)