Bug fix for deserialize model issue and added unit tests for python client

[geekerzp]

• Fixed deserializing model issue in python client.
  Before fixing, we import the models in swagger.py like this from models import *.
  So we can get the model class like this pet.Pet (the first pet is the module name).
  But in swagger.py 214 line objClass = eval(objClass + '.' + objClass),
  https://github.com/swagger-api/swagger-codegen/pull/680/files#diff-7356954fd07cc52ba5ac73153eb27cd8L214.
  It will evaluate Pet.Pet to get the model class which is incorrect.
  After fixing, we import the models in swagger.py like this import models.
  We can get the model class like this models.Pet.
  objClass = eval('models.' + objClass) will get the correct class.
• Added unit testing for python client and added pom.xml.
  Below is the result:

  SwaggerPetstore-python(develop_2.0_python_testing) ✗: mvn integration-test -rf :PythonPetstoreClientTests
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Python Swagger Petstore Client 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.8:copy-dependencies (default) @ PythonPetstoreClientTests ---
[INFO]
[INFO] --- exec-maven-plugin:1.2.1:exec (nose-install) @ PythonPetstoreClientTests ---
Requirement already satisfied (use --upgrade to upgrade): nose in /usr/local/lib/python2.7/site-packages
[INFO]
[INFO] --- exec-maven-plugin:1.2.1:exec (nose-test) @ PythonPetstoreClientTests ---
test_1_add_pet (tests.test_pet_api.PetApiTests) ... ok
test_2_get_pet_by_id (tests.test_pet_api.PetApiTests) ... ok
test_3_update_pet (tests.test_pet_api.PetApiTests) ... ok
test_4_find_pets_by_status (tests.test_pet_api.PetApiTests) ... ok
test_5_find_pets_by_tags (tests.test_pet_api.PetApiTests) ... ok
test_6_update_pet_with_form (tests.test_pet_api.PetApiTests) ... ok
test_7_upload_file (tests.test_pet_api.PetApiTests) ... ok
test_8_delete_pet (tests.test_pet_api.PetApiTests) ... ok

----------------------------------------------------------------------
Ran 8 tests in 14.839s

OK
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 17.996 s
[INFO] Finished at: 2015-04-23T18:18:03+08:00
[INFO] Final Memory: 11M/156M
[INFO] ------------------------------------------------------------------------

[fehguy]

awesome contrib as always, and special (?) thanks for the hello kitty.