Allow to keep directories in case of error.

Default is to remove.

slapos/recipe/build.py

@@ -102,6 +102,8 @@ def guessPlatform():
   return target
 
 
+TRUE_LIST = ('y', 'on', 'yes', 'true', '1')
+
 class Script:
   """Free script building system"""
   def _checkPromise(self, promise_key, location):
@@ -247,7 +249,11 @@ class Script:
       self.options[k] = self.options.get(k, '').strip()
     self.options['script'] = self.options.get('script', self.script) % \
       self.options
-
+    if self.options.get('keep-on-error', '').strip().lower() in TRUE_LIST:
+      self.logger.debug('Keeping directories in case of errors')
+      self.keep_on_error = True
+    else:
+      self.keep_on_error = False
   def getEnvironment(self):
     # prepare cool dictionary
     wanted_env = {}
@@ -293,8 +299,11 @@ class Script:
     finally:
       for d in self.cleanup_dir_list:
         if os.path.exists(d):
+          if not self.keep_on_error:
             self.logger.debug('Cleanup directory %r' % d)
             shutil.rmtree(d)
+          else:
+            self.logger.info('Left directory %r as requested' % d)
 
     return [self.options['location']]