try using setuptools_scm for automatic versioning based on py-* tags (#187)

* try using setuptools_scm for automatic versioning based on py-* tags

* circument problem with pip-wheel isolation and setuptoosl_scm

* always provide version, address @flub comment

python/tests/package_wheels.py

@@ -0,0 +1,15 @@
+
+import os
+import sys
+import subprocess
+
+
+if __name__ == "__main__":
+    assert len(sys.argv) == 2
+    wheelhousedir = sys.argv[1]
+    # pip wheel will build in an isolated tmp dir that does not have git
+    # history so setuptools_scm can not automatically determine a
+    # version there. So pass in the version through an env var.
+    version = subprocess.check_output(["python", "setup.py", "--version"]).strip().split(b"\n")[-1]
+    os.environ["SETUPTOOLS_SCM_PRETEND_VERSION"] = version.decode("ascii")
+    subprocess.check_call(("pip wheel . -w %s" % wheelhousedir).split())