Rework eggtest to use eggs installed by buildout

This should address two issues:
 1. Allow using a custom python interpreter where all eggs dependencies would already be installed.
 2. The test names did not have stable name, because they were the full path of the folder, which varies from one test node to another. This depends on changes in the profile done in nexedi/slapos!309 .

This changes the internals of `EggTestSuite` so other tests reusing it ( I think we only have [`deploy-test`](https://lab.nexedi.com/nexedi/slapos/blob/41191a29cd16af13b2667d1979f35628c6065fde/software/erp5testnode/testsuite/deploy-test/runTestSuite.py#L151-154) ) will have to be updated once a new `erp5.util` is released. @luke I guess this won't be a problem and this would allow to fix that second issue for deploy test as well, so I did not consider being backward compatible here.

/cc @rafael @alain.takoudjou 


/reviewed-on nexedi/erp5!619

erp5/util/testsuite/__init__.py

@@ -223,16 +223,14 @@ class EggTestSuite(TestSuite):
     print test
     original_dir = os.getcwd()
     try:
-      os.chdir(test)
+      os.chdir(self.egg_test_path_dict[test])
       return self.runUnitTest(test)
     finally:
       os.chdir(original_dir)
 
   def runUnitTest(self, *args, **kw):
     try:
-      # (FIXME) The python should be provided by environment with 
-      #         appropriated configuration.
-      runUnitTest = "python setup.py test"
+      runUnitTest = "{python} setup.py test".format(python=self.python_interpreter)
       args = tuple(shlex.split(runUnitTest))
       status_dict = self.spawn(*args, **kw)
     except SubprocessError, e:
@@ -263,10 +261,7 @@ class EggTestSuite(TestSuite):
     return status_dict
 
   def getTestList(self):
-    # (FIXME) The test name should be nicer in order to provide a good report.
-    #         On task distribution.
-    source_code_to_test = os.environ.get("SOURCE_CODE_TO_TEST", '.')
-    return source_code_to_test.split(",")
+    return self.egg_test_path_dict.keys()
 
 def runTestSuite():
   parser = argparse.ArgumentParser(description='Run a test suite.')
@@ -287,18 +282,24 @@ def runTestSuite():
   parser.add_argument('--frontend_url',
                       help='The url of the frontend of this test node',
                       default=None)
+  parser.add_argument('--python_interpreter',
+                      help='Path to python interpreter used to run the test suite',
+                      default='python')
   parser.add_argument('--source_code_path_list',
-                      help='List of Eggs folders to test, splited by commam',
+                      help='Coma separated list of Eggs folders to test',
                       default='.')
 
   args = parser.parse_args()
   master = taskdistribution.TaskDistributor(args.master_url)
-  os.environ.setdefault("SOURCE_CODE_TO_TEST", args.source_code_path_list)
   test_suite_title = args.test_suite_title or args.test_suite
   revision = args.revision
   suite = EggTestSuite(1, test_suite=args.test_suite,
                     node_quantity=args.node_quantity,
-                    revision=revision)
+                    revision=revision,
+                    python_interpreter=args.python_interpreter,
+                    egg_test_path_dict={os.path.basename(path): path
+                        for path in args.source_code_path_list.split(',')},
+                    )
 
   test_result = master.createTestResult(revision, suite.getTestList(),
     args.test_node_title, suite.allow_restart, test_suite_title,