chore: refactor python tests to use unittest (#2414)

Move every test to a method on DenoTestCase.
test.py is a single TestSuite of every TestCase.

Add a Spawn context manager for http_server,
this is explicitly used where it's needed.
Each python test file can now be run independently
without needing to manually run http_server.

Add --help and consistent flags using argparse for
each python test, including --failfast.

Use ColorTextTestRunner so that '... ok' is green.

tools/fetch_test.py

@@ -2,29 +2,29 @@
 # Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
 import os
 import sys
-from util import mkdtemp, tests_path, run_output, green_ok
 import shutil
 
+from http_server import spawn
+from util import DenoTestCase, mkdtemp, tests_path, run_output, test_main
 
-def fetch_test(deno_exe):
-    sys.stdout.write("fetch_test...")
-    sys.stdout.flush()
 
-    deno_dir = mkdtemp()
-    try:
-        t = os.path.join(tests_path, "006_url_imports.ts")
-        output = run_output([deno_exe, "fetch", t],
-                            merge_env={"DENO_DIR": deno_dir})
-        assert output == ""
-        # Check that we actually did the prefetch.
-        os.path.exists(
-            os.path.join(deno_dir,
-                         "deps/http/localhost_PORT4545/tests/subdir/mod2.ts"))
-    finally:
-        shutil.rmtree(deno_dir)
-
-    print green_ok()
+class FetchTest(DenoTestCase):
+    def test_fetch(self):
+        deno_dir = mkdtemp()
+        try:
+            t = os.path.join(tests_path, "006_url_imports.ts")
+            output = run_output([self.deno_exe, "fetch", t],
+                                merge_env={"DENO_DIR": deno_dir})
+            assert output == ""
+            # Check that we actually did the prefetch.
+            os.path.exists(
+                os.path.join(
+                    deno_dir,
+                    "deps/http/localhost_PORT4545/tests/subdir/mod2.ts"))
+        finally:
+            shutil.rmtree(deno_dir)
 
 
 if __name__ == "__main__":
-    fetch_test(sys.argv[1])
+    with spawn():
+        test_main()