Fix version handling

See https://packaging.python.org/guides/single-sourcing-package-version/.

bin/etherpump

@@ -2,7 +2,7 @@
 
 import sys
 
-from etherpump import VERSION
+from etherpump import __VERSION__
 
 usage = """Usage:
     etherpump CMD
@@ -36,7 +36,7 @@ try:
         print(usage)
         sys.exit(0)
     elif any(arg in args for arg in ['--version', '-v']):
-        print('etherpump {}'.format(VERSION))
+        print('etherpump {}'.format(__VERSION__))
         sys.exit(0)
 
 except IndexError:

etherpump/__init__.py

@@ -1,4 +1,5 @@
 import os
 
 DATAPATH = os.path.join(os.path.dirname(os.path.realpath(__file__)), "data")
-VERSION = '0.0.2'
+
+__VERSION__ = '0.0.2'

setup.py

@@ -1,15 +1,35 @@
 #!/usr/bin/env python3
 
+import codecs
+import os
+import re
+
 from setuptools import find_packages, setup
 
-from etherpump import VERSION
+
+def read(*parts):
+    current_file = os.path.abspath(os.path.dirname(__file__))
+    with codecs.open(os.path.join(current_file, *parts), 'r') as fp:
+        return fp.read()
+
+
+def find_version(*file_paths):
+    version_file = read(*file_paths)
+    version_match = re.search(
+        r"^__VERSION__ = ['\"]([^'\"]*)['\"]", version_file, re.M
+    )
+    if version_match:
+        return version_match.group(1)
+    raise RuntimeError("Unable to find version string.")
+
 
 with open('README.md', 'r') as handle:
     long_description = handle.read()
 
+
 setup(
     name='etherpump',
-    version=VERSION,
+    version=find_version('etherpump', '__init__.py'),
     author='Varia members',
     author_email='info@varia.zone',
     packages=find_packages(),