Fix DeprecationWarning: invalid escape sequence in versioneer.py

Signed-off-by: Mickaël Schoentgen <contact@tiger-222.fr>

Author: BoboTiG

versioneer.py

@@ -464,7 +464,7 @@ def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False):
             print("unable to run %s (error)" % dispcmd)
         return None
     return stdout
-LONG_VERSION_PY['git'] = '''
+LONG_VERSION_PY['git'] = r'''
 # This file helps to compute a version number in source trees obtained from
 # git-archive tarball (such as those provided by githubs download-from-tag
 # feature). Distribution tarballs (built by setup.py sdist) and build