[molecule] add support for MOLECULE_TMPDIR environment variable (defaulting to /var/tmp), so that user can override it

molecule/settings.py

@@ -32,9 +32,11 @@ class Constants(dict):
     def load(self):
         ETC_DIR = '/etc'
         CONFIG_FILE_NAME = 'molecule.conf'
+        TMP_DIR = os.getenv("MOLECULE_TMPDIR", "/var/tmp")
 
         mysettings = {
             'config_file': os.path.join(ETC_DIR, CONFIG_FILE_NAME),
+            'tmp_dir': TMP_DIR,
         }
 
         self.clear()
@@ -52,6 +54,7 @@ class Configuration(dict):
             mysettings = {}
         settings = {
             'version': VERSION,
+            'tmp_dir': self.Constants['tmp_dir'],
             'chroot_compressor': "/usr/bin/mksquashfs",
             'iso_builder': "/usr/bin/mkisofs",
             'mirror_syncer': "/usr/bin/rsync",

molecule/utils.py

@@ -126,10 +126,12 @@ def empty_dir(dest_dir):
 
 def mkdtemp(suffix=''):
     """
-    Generate a reliable temporary directory inside /var/tmp starting with
-    "molecule".
+    Generate a reliable temporary directory inside MOLECULE_TMPDIR
+    env var (/var/tmp) starting with "molecule".
     """
-    return tempfile.mkdtemp(prefix = "molecule", dir = "/var/tmp",
+    import molecule.settings
+    tmp_dir = molecule.settings.Configuration()['tmp_dir']
+    return tempfile.mkdtemp(prefix = "molecule", dir = tmp_dir,
         suffix = suffix)
 
 # using subprocess.call to not care about wildcards