Better versioning: no silly version files, but wrong ver in development

Small price to pay.

setup.py

@@ -7,28 +7,12 @@ from subprocess import STDOUT, check_output, CalledProcessError
 from collections.abc import Mapping
 import re
 import sys
-import os
 
 
 if sys.version_info < (3, 4):
     print("Python 3.4 or newer is required")
     sys.exit(1)
 
-version_py = os.path.join(os.path.dirname(__file__), 'ocrmypdf', 'version.py')
-try:
-    version_git = check_output(["git", "describe"],
-                               universal_newlines=True).rstrip()
-    version_git = version_git.replace('-g', '+n')
-    version_git = version_git.replace('-', '.dev')
-except Exception:
-    with open(version_py, 'r') as fh:
-        version_git = fh.read().strip().split('=')[-1].replace('"', '')
-
-version_msg = "# Do not edit this file"
-with open(version_py, 'w') as fh:
-    fh.write('\n'.join([version_msg, '__version__="' + version_git + '"']))
-
-
 missing_program = '''
 The program '{program}' could not be executed or was not found on your
 system PATH.
@@ -198,7 +182,6 @@ tests_require = open('test_requirements.txt').read().splitlines()
 
 setup(
     name='ocrmypdf',
-    version="{ver}".format(ver=version_git),
     description='OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched',
     url='https://github.com/jbarlow83/OCRmyPDF',
     author='James R. Barlow',
@@ -222,6 +205,10 @@ setup(
         "Topic :: Text Processing :: Indexing",
         "Topic :: Text Processing :: Linguistic",
         ],
+    setup_requires=[
+        'setuptools_scm'
+    ],
+    use_scm_version={'version_scheme': 'post-release'},
     install_requires=[
         'ruffus',
         'Pillow',