build: standardize version number placement

lti_consumer/__init__.py

@@ -3,3 +3,5 @@ Runtime will load the XBlock class from here.
 """
 from .lti_xblock import LtiConsumerXBlock
 from .apps import LTIConsumerApp
+
+__version__ = '3.1.0'

setup.py

 """Setup for lti_consumer XBlock."""
 
 import os
+import re
 
 from setuptools import setup, find_packages
 
@@ -47,9 +48,26 @@ def is_requirement(line):
 with open('README.rst') as _f:
     long_description = _f.read()
 
+
+def get_version(file_path):
+    """
+    Extract the version string from the file at the given relative path fragments.
+    """
+    filename = os.path.join(os.path.dirname(__file__), file_path)
+    with open(filename, encoding='utf-8') as opened_file:
+        version_file = opened_file.read()
+        version_match = re.search(r"(?m)^__version__ = ['\"]([^'\"]+)['\"]", version_file)
+    if version_match:
+        return version_match.group(1)
+    raise RuntimeError('Unable to find version string.')
+
+
+VERSION = get_version("lti_consumer/__init__.py")
+
+
 setup(
     name='lti-consumer-xblock',
-    version='3.1.0',
+    version=VERSION,
     author='Open edX project',
     author_email='oscm@edx.org',
     description='This XBlock implements the consumer side of the LTI specification.',