Asset Fetcher: make the cache dirs visible

The asset fetchers cache directories are system wide, and not test
specific.  They're available at the test only for convenience.

They relate much more to the the other data directories, and deserve
to be visible by users alongside the other data directories.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/core/data_dir.py

@@ -199,6 +199,18 @@ def create_job_logs_dir(base_dir=None, unique_id=None):
                   % (logdir))
 
 
+def get_cache_dirs():
+    """
+    Returns the list of cache dirs, according to configuration and convention
+    """
+    cache_dirs = settings.settings.get_value('datadir.paths', 'cache_dirs',
+                                             key_type=list, default=[])
+    datadir_cache = os.path.join(get_data_dir(), 'cache')
+    if datadir_cache not in cache_dirs:
+        cache_dirs.append(datadir_cache)
+    return cache_dirs
+
+
 class _TmpDirTracker(Borg):
 
     def __init__(self):

avocado/core/test.py

@@ -567,12 +567,7 @@ class Test(unittest.TestCase, TestData):
         Returns a list of cache directories as set in config file.
         """
         if self.__cache_dirs is None:
-            cache_dirs = settings.get_value('datadir.paths', 'cache_dirs',
-                                            key_type=list, default=[])
-            datadir_cache = os.path.join(data_dir.get_data_dir(), 'cache')
-            if datadir_cache not in cache_dirs:
-                cache_dirs.append(datadir_cache)
-            self.__cache_dirs = cache_dirs
+            self.__cache_dirs = data_dir.get_cache_dirs()
         return self.__cache_dirs
 
     @property

avocado/plugins/config.py

@@ -70,3 +70,4 @@ class Config(CLICmd):
             LOG_UI.debug('    tests    ' + data_dir.get_test_dir())
             LOG_UI.debug('    data     ' + data_dir.get_data_dir())
             LOG_UI.debug('    logs     ' + data_dir.get_logs_dir())
+            LOG_UI.debug('    cache    ' + ", ".join(data_dir.get_cache_dirs()))