wrap magento call in mappers into try and catch
Merge branch 'master' of git://github.com/akeneo/MagentoConnectorBundle

* 'master' of git://github.com/akeneo/MagentoConnectorBundle: (42 commits)
  Improve MagentoItemStepSpec #191
  Add full export job fixture #189
  Update HasValidCredentialsValidatorSpec #181
  Fix bug - exception is well catched and error is personnalized  #181
  Refactor specs to use short syntax
  Fix doc in MagentoMapper (remove registry mention) #181
  Fix bug bad refactor of property
  Refactoring : use of short tags for array
  Added constant for unknown versions of magento
  Fix php specs due to refactoring
  Fix bugs due to refactoring
  Return default magento version when core access is denied
  Renamed functions and remove not used one
  Improve specs
  CS pb in Abstract guesser #175
  Update Abstract guesser #175
  CHANGELOG updated #175
  Add version 1.9 an 1.14 magento support #175
  Delete file created by phpspec
  Refactoring for PR #160
  ...