Add 'code-block' and revise tab

This commit inserts '.. code-block::' and revises tab to 4 spaces.

Change-Id: Ic36444f101cc8a560c1cfa67dffdf64956c2bb99
diff --git a/doc/source/microversion_testing.rst b/doc/source/microversion_testing.rst
index bff18f8..dc73ef2 100644
--- a/doc/source/microversion_testing.rst
+++ b/doc/source/microversion_testing.rst
@@ -24,7 +24,9 @@
   * max_microversion
 
   Those should be defined under respective section of each service.
-  For example::
+  For example:
+
+  .. code-block:: ini
 
       [compute]
       min_microversion = None
@@ -42,7 +44,9 @@
 api_version_utils.check_skip_with_microversion function can be used
 to automatically skip the tests which do not fall under configured
 Microversion range.
-For example::
+For example:
+
+.. code-block:: python
 
     class BaseTestCase1(api_version_utils.BaseMicroversionTest):
 
@@ -65,7 +69,9 @@
 to send with API request.
 api_version_utils.select_request_microversion function can be used
 to select the appropriate Microversion which will be used for API request.
-For example::
+For example:
+
+.. code-block:: python
 
     @classmethod
     def resource_setup(cls):
@@ -87,7 +93,9 @@
 Also Microversion header name needs to be defined on service clients which
 should be constant because it is not supposed to be changed by project
 as per API contract.
-For example::
+For example:
+
+.. code-block:: python
 
       COMPUTE_MICROVERSION = None
 
@@ -96,7 +104,9 @@
 
 Now test class can set the selected Microversion on required service clients
 using fixture which can take care of resetting the same once tests is completed.
-For example::
+For example:
+
+.. code-block:: python
 
     def setUp(self):
         super(BaseTestCase1, self).setUp()
@@ -105,7 +115,9 @@
 
 Service clients needs to add set Microversion in API request header which
 can be done by overriding the get_headers() method of rest_client.
-For example::
+For example:
+
+.. code-block:: python
 
       COMPUTE_MICROVERSION = None
 
@@ -136,7 +148,9 @@
 
 For example:
 
-Below test is applicable for Microversion from 2.2 till 2.9::
+Below test is applicable for Microversion from 2.2 till 2.9:
+
+.. code-block:: python
 
     class BaseTestCase1(api_version_utils.BaseMicroversionTest,
                         tempest.test.BaseTestCase):
@@ -150,7 +164,9 @@
 
         [..]
 
-Below test is applicable for Microversion from 2.10 till latest::
+Below test is applicable for Microversion from 2.10 till latest:
+
+.. code-block:: python
 
     class Test2(BaseTestCase1):
         min_microversion = '2.10'
@@ -159,8 +175,6 @@
         [..]
 
 
-
-
 Notes about Compute Microversion Tests
 """"""""""""""""""""""""""""""""""""""