Feature: custom virtual environment directories

Currently, users are allowed to define virtual environments in
`settings.BASE_VENV_PATH` only, because that's the only place
Tower looks for virtual environments. This feature allows users
to custom define the directory paths, using API or UI, to look
for virtual environments. Tower aggregates virtual environments
from all these paths, except environments with special name `awx`.

Signed-off-by: Vismay Golwala <vgolwala@redhat.com>

awx/conf/fields.py

@@ -1,4 +1,5 @@
 # Python
+import os
 import logging
 import urllib.parse as urlparse
 from collections import OrderedDict
@@ -96,6 +97,26 @@ class StringListBooleanField(ListField):
         self.fail('type_error', input_type=type(data))
 
 
+class StringListPathField(StringListField):
+
+    default_error_messages = {
+        'type_error': _('Expected list of strings but got {input_type} instead.'),
+        'path_error': _('{path} is not a valid path choice.'),
+    }
+
+    def to_internal_value(self, paths):
+        if isinstance(paths, (list, tuple)):
+            for p in paths:
+                if not isinstance(p, str):
+                    self.fail('type_error', input_type=type(p))
+                if not os.path.exists(p):
+                    self.fail('path_error', path=p)
+
+            return super(StringListPathField, self).to_internal_value(sorted({os.path.normpath(path) for path in paths}))
+        else:
+            self.fail('type_error', input_type=type(paths))
+
+
 class URLField(CharField):
 
     def __init__(self, **kwargs):