Fix python dockerpy tests

* Refactor packaging so unittest discovery works
* Refactor tests to use python3-docker.rpm that ships with Fedora32
* Flush image cache between tests suites
* Update documentation to reflect changes

Outstanding issue:
* client.get_image() does not fail if image does not exist

Signed-off-by: Jhon Honce <jhonce@redhat.com>

test/python/dockerpy/tests/common.py

@@ -0,0 +1,105 @@
+import os
+import pathlib
+import subprocess
+import sys
+import time
+
+from docker import APIClient
+
+from . import constant
+
+alpineDict = {
+    "name": "docker.io/library/alpine:latest",
+    "shortName": "alpine",
+    "tarballName": "alpine.tar"
+}
+
+
+def get_client():
+    client = APIClient(base_url="http://localhost:8080", timeout=15)
+    return client
+
+
+client = get_client()
+
+
+def podman():
+    binary = os.getenv("PODMAN_BINARY")
+    if binary is None:
+        binary = "../../../bin/podman"
+    return binary
+
+
+def restore_image_from_cache(TestClass):
+    alpineImage = os.path.join(constant.ImageCacheDir,
+                               alpineDict["tarballName"])
+    if not os.path.exists(alpineImage):
+        os.makedirs(constant.ImageCacheDir, exist_ok=True)
+        client.pull(constant.ALPINE)
+        image = client.get_image(constant.ALPINE)
+        tarball = open(alpineImage, mode="wb")
+        for frame in image:
+            tarball.write(frame)
+        tarball.close()
+    else:
+        subprocess.run(
+            [podman(), "load", "-i", alpineImage],
+            shell=False,
+            stdin=subprocess.DEVNULL,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+            check=True,
+        )
+
+
+def flush_image_cache(TestCase):
+    for f in pathlib.Path(constant.ImageCacheDir).glob("*"):
+        f.unlink(f)
+
+
+def run_top_container():
+    c = client.create_container(image=constant.ALPINE,
+                                command='/bin/sleep 5',
+                                name=constant.TOP)
+    client.start(container=c.get("Id"))
+    return c.get("Id")
+
+
+def enable_sock(TestClass):
+    TestClass.podman = subprocess.Popen(
+        [
+            podman(), "system", "service", "tcp:localhost:8080",
+            "--log-level=debug", "--time=0"
+        ],
+        shell=False,
+        stdin=subprocess.DEVNULL,
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.DEVNULL,
+    )
+    time.sleep(2)
+
+
+def terminate_connection(TestClass):
+    TestClass.podman.terminate()
+    stdout, stderr = TestClass.podman.communicate(timeout=0.5)
+    if stdout:
+        print("\nService Stdout:\n" + stdout.decode('utf-8'))
+    if stderr:
+        print("\nService Stderr:\n" + stderr.decode('utf-8'))
+
+    if TestClass.podman.returncode > 0:
+        sys.stderr.write("podman exited with error code {}\n".format(
+            TestClass.podman.returncode))
+        sys.exit(2)
+
+
+def remove_all_containers():
+    containers = client.containers(quiet=True)
+    for c in containers:
+        client.remove_container(container=c.get("Id"), force=True)
+
+
+def remove_all_images():
+    allImages = client.images()
+    for image in allImages:
+        client.remove_image(image, force=True)