Update imports to be explicitly relative (#296)

In python 3, imports are absolute by default. By adding from __future__ import absolute_import, we ensure that python 2 adopts this behavior too.

Author: jameslynnwu

apitools/gen/extended_descriptor.py

@@ -416,6 +416,8 @@ def PrintPreamble(self, package, version, file_descriptor):
         self.__printer('# NOTE: This file is autogenerated and should not be '
                        'edited by hand.')
         self.__printer()
+        self.__printer('from __future__ import absolute_import')
+        self.__printer()
         self.__PrintAdditionalImports(file_descriptor.additional_imports)
         self.__printer()
         self.__printer("package = '%s'", file_descriptor.package)

apitools/gen/gen_client_lib.py

@@ -168,12 +168,14 @@ def WriteInit(self, out):
         else:
             printer('"""Package marker file."""')
         printer()
+        printer('from __future__ import absolute_import')
+        printer()
         printer('import pkgutil')
         printer()
         if self.__init_wildcards_file:
             printer('from %s import *', self.__base_files_package)
             if self.__root_package == '.':
-                import_prefix = ''
+                import_prefix = '.'
             else:
                 import_prefix = '%s.' % self.__root_package
             printer('from %s%s import *',

apitools/gen/gen_client_test.py

@@ -73,6 +73,8 @@ def testGenClient_SimpleDocEmptyInit(self):
             init_file = _GetContent(os.path.join(tmp_dir_path, '__init__.py'))
             self.assertEqual("""\"""Package marker file.\"""
 
+from __future__ import absolute_import
+
 import pkgutil
 
 __path__ = pkgutil.extend_path(__path__, __name__)

apitools/gen/service_registry.py

@@ -200,6 +200,9 @@ def WriteFile(self, printer):
                 client_info.package, client_info.version)
         printer('# NOTE: This file is autogenerated and should not be edited '
                 'by hand.')
+        printer()
+        printer('from __future__ import absolute_import')
+        printer()
         printer('from %s import base_api', self.__base_files_package)
         if self.__root_package:
             import_prefix = 'from {0} '.format(self.__root_package)

samples/bigquery_sample/bigquery_v2/__init__.py

@@ -1,5 +1,7 @@
 """Package marker file."""
 
+from __future__ import absolute_import
+
 import pkgutil
 
 __path__ = pkgutil.extend_path(__path__, __name__)

samples/bigquery_sample/bigquery_v2/bigquery_v2_client.py

@@ -1,5 +1,8 @@
 """Generated client library for bigquery version v2."""
 # NOTE: This file is autogenerated and should not be edited by hand.
+
+from __future__ import absolute_import
+
 from apitools.base.py import base_api
 from samples.bigquery_sample.bigquery_v2 import bigquery_v2_messages as messages
 

samples/bigquery_sample/bigquery_v2/bigquery_v2_messages.py

@@ -4,6 +4,8 @@
 """
 # NOTE: This file is autogenerated and should not be edited by hand.
 
+from __future__ import absolute_import
+
 from apitools.base.protorpclite import messages as _messages
 from apitools.base.py import encoding
 from apitools.base.py import extra_types

samples/dns_sample/dns_v1/__init__.py

@@ -1,5 +1,7 @@
 """Package marker file."""
 
+from __future__ import absolute_import
+
 import pkgutil
 
 __path__ = pkgutil.extend_path(__path__, __name__)

samples/dns_sample/dns_v1/dns_v1_client.py

@@ -1,5 +1,8 @@
 """Generated client library for dns version v1."""
 # NOTE: This file is autogenerated and should not be edited by hand.
+
+from __future__ import absolute_import
+
 from apitools.base.py import base_api
 from samples.dns_sample.dns_v1 import dns_v1_messages as messages
 

samples/dns_sample/dns_v1/dns_v1_messages.py

@@ -5,6 +5,8 @@
 """
 # NOTE: This file is autogenerated and should not be edited by hand.
 
+from __future__ import absolute_import
+
 from apitools.base.protorpclite import messages as _messages