Fix unit tests for elements

It looks like we dropped running these probably when we moved the
elements around.  For testtools to find the test scripts we need to
add the __init__.py files to make the directories look like modules.
Also prevent copying any .pyc or cache files in as hooks.

Change-Id: I66d5f6ee62cc4d9ee14c64e819b4db57d035d09f

diskimage_builder/elements/cache-url/tests/test_cache_url.py

@@ -27,15 +27,15 @@ class TestCacheUrl(base.ScriptTestBase):
         source = 'http://fake/url'
         # Write fake data to the target file and return success
         self._stub_script('curl', 'echo "test" > ${3:7:100}\necho 200')
-        self._run_command(['elements/cache-url/bin/cache-url',
-                           source,
-                           target])
+        self._run_command(
+            ['diskimage_builder/elements/cache-url/bin/cache-url',
+             source, target])
         self.assertTrue(os.path.exists(target))
         modification_time = os.path.getmtime(target)
         # Make sure that the timestamp would change if the file does
         time.sleep(1)
         self._stub_script('curl', 'echo "304"')
-        self._run_command(['elements/cache-url/bin/cache-url',
-                           source,
-                           target])
+        self._run_command(
+            ['diskimage_builder/elements/cache-url/bin/cache-url',
+             source, target])
         self.assertEqual(modification_time, os.path.getmtime(target))

diskimage_builder/lib/common-functions

@@ -111,11 +111,15 @@ function generate_hooks () {
 
         for dir in $(find $element_dir \
                           -follow -mindepth 1 -maxdepth 1 \
-                          -type d -not -name tests); do
+                          -type d \
+                          -not -name tests \
+                          -not -name __pycache__); do
             copy_hooks_not_overwrite $dir
         done
         for file in $(find $element_dir \
-                           -follow -maxdepth 1 -type f); do
+                           -follow -maxdepth 1 \
+                           -type f \
+                           -not -name '*.pyc'); do
             cp -t $TMP_HOOKS_PATH -a $file
         done
     done