devtest: Make Python tests their own type of devtest

Like the example test, the Python-based test is now codified. The
"special sauce" for Python tests revolves around the fact that they
require the Python API, so we have to gracefully fail if the Python API
was never enabled, but hard-fail when the Python API is enabled, but not
working.

This creates a new type of devtest (UHDPythonTestCase) and moves
uhd_python_api_test over to the new type.

host/tests/devtest/gpio_test.py

@@ -37,4 +37,3 @@ class gpio_test(uhd_example_test_case):
             print(app.stderr)
         self.report_example_results(test_name, run_results)
         return run_results
-

host/tests/devtest/python_api_test.py

@@ -8,35 +8,16 @@
 
 import os
 from uhd_test_base import shell_application
-from uhd_test_base import uhd_test_case
-try:
-    import uhd
-except ImportError:
-    uhd = None
+from uhd_test_base import UHDPythonTestCase
 
-# For what we're doing here, ruamel.yaml and yaml are compatible, and we'll use
-# whatever we can find
-try:
-    from ruamel import yaml
-except:
-    import yaml
-
-
-class uhd_python_api_test(uhd_test_case):
+class uhd_python_api_test(UHDPythonTestCase):
     """ Run multi_usrp_test """
-    def test_api(self):
+    test_name = 'uhd_python_api_test'
+
+    def run_test(self, test_name, test_args):
         """
         Run test and report results.
         """
-        if uhd is None:
-            print("UHD module not found -- checking for Python API")
-            config_info_app = shell_application('uhd_config_info')
-            config_info_app.run(['--enabled-components'])
-            if "Python API" in config_info_app.stdout:
-                raise RuntimeError("Python API enabled, but cannot load uhd module!")
-            print("Skipping test, Python API not installed.")
-            self.report_result("python_api_tester", 'status', 'Skipped')
-            return
         devtest_src_dir = os.getenv('_UHD_DEVTEST_SRC_DIR', '')
         multi_usrp_test_path = \
             os.path.join(devtest_src_dir, 'multi_usrp_test.py')
@@ -71,11 +52,4 @@ class uhd_python_api_test(uhd_test_case):
                 'status',
                 'Passed' if run_results['passed'] else 'Failed',
             )
-        self.assertTrue(
-            run_results['passed'],
-            msg="Errors occurred during test python_api_test. "
-                "Check log file for details.\n"
-                "Run results:\n{r}".format(
-                    r=yaml.dump(run_results, default_flow_style=False)
-                )
-        )
+        return run_results

host/tests/devtest/uhd_test_base.py

@@ -16,8 +16,9 @@ import unittest
 import re
 import time
 import logging
+import importlib
 from subprocess import Popen, PIPE
-# For what we're doing here, ruamel.yaml and yaml are copatible, and we'll use
+# For what we're doing here, ruamel.yaml and yaml are compatible, and we'll use
 # whatever we can find
 try:
     from ruamel import yaml
@@ -105,7 +106,6 @@ class uhd_test_case(unittest.TestCase):
         """
         Override this to add own setup code per test.
         """
-        pass
 
     def setUp(self):
         self.name = self.__class__.__name__
@@ -146,7 +146,6 @@ class uhd_test_case(unittest.TestCase):
 
     def tear_down(self):
         """Nothing to do."""
-        pass
 
     def tearDown(self):
         self.tear_down()
@@ -178,7 +177,6 @@ class uhd_example_test_case(uhd_test_case):
         """
         Override this to add specific setup code.
         """
-        pass
 
     def set_up(self):
         """Called by the unit testing framework on tests. """
@@ -248,12 +246,68 @@ class uhd_example_test_case(uhd_test_case):
                     or (self.usrp_info['product'] in test_args.get('products', [])):
                 run_results = self.run_test(test_name, test_args)
                 passed = bool(run_results)
+                errors = ''
                 if isinstance(run_results, dict):
                     passed = run_results['passed']
-                errors = run_results.pop("errors", None)
-                if not passed:
-                    print("Error log:", file=sys.stderr)
-                    print(errors)
+                    errors = run_results.pop("errors", None)
+                    if not passed:
+                        print("Error log:", file=sys.stderr)
+                        print(errors)
+                self.assertTrue(
+                    passed,
+                    msg="Errors occurred during test `{t}'. "
+                        "Check log file for details.\n"
+                        "Run results:\n{r}".format(
+                            t=test_name,
+                            r=yaml.dump(run_results, default_flow_style=False)
+                        )
+                )
+
+class UHDPythonTestCase(uhd_test_case):
+    """
+    Helper class for Python test cases. These require the uhd module, but that's
+    not always available. We thus test for its existence.
+    """
+
+    def run_test(self, test_name, test_args):
+        """
+        Override this to run the actual example.
+
+        Needs to return either a boolean or a dict with key 'passed' to determine
+        pass/fail.
+        """
+        raise NotImplementedError
+
+    def test_all(self):
+        """
+        Hook for test runner. Needs to be a class method that starts with 'test'.
+        Calls run_test().
+        """
+        try:
+            self.uhd = importlib.import_module('uhd')
+        except ImportError:
+            print("UHD module not found -- checking for Python API")
+            config_info_app = shell_application('uhd_config_info')
+            config_info_app.run(['--enabled-components'])
+            if "Python API" in config_info_app.stdout:
+                raise RuntimeError("Python API enabled, but cannot load uhd module!")
+            self.log.info("Skipping test, Python API not installed.")
+            self.report_result("python_api_tester", 'status', 'Skipped')
+            return
+        # Now: The actual test
+        test_params = getattr(self, 'test_params', {'default': {},})
+        for test_name, test_args in test_params.items():
+            time.sleep(15) # Wait for X300 devices to reclaim them
+            if 'products' not in test_args \
+                    or (self.usrp_info['product'] in test_args.get('products', [])):
+                run_results = self.run_test(test_name, test_args)
+                passed = bool(run_results)
+                if isinstance(run_results, dict):
+                    passed = run_results['passed']
+                    errors = run_results.pop("errors", None)
+                    if not passed:
+                        print("Error log:", file=sys.stderr)
+                        print(errors)
                 self.assertTrue(
                     passed,
                     msg="Errors occurred during test `{t}'. "