Add support for nox dirs

We use nox in a lot of places now. We should support that.

Change-Id: I21a592b4cea3e4acc7540f00504322c7e6a6edb8

README.rst

@@ -5,14 +5,14 @@ ttrun
 Simple CLI to run testtools tests
 
 In a `testrepository` based workflow, sometimes you want/need to run individual
-tests. Additionally, someitmes you want to use a pre-existing tox virtualenv
+tests. Additionally, someitmes you want to use a pre-existing tox or nox virtualenv
 to do so. Or, at least, I do.
 
 Typing
 
 .. code-block:: bash
 
-  .tox/py27/bin/python -m testtools.run some.test
+  .nox/py27/bin/python -m testtools.run some.test
 
 Got boring. So this is a simple wrapper.
 
@@ -24,12 +24,12 @@ It has two modes.
 
 Will run that test with the system python.
 
-If you want to re-use a tox virtualenv.
+If you want to re-use a nox virtualenv.
 
 .. code-block:: bash
 
   ttrun -epy27 some.test
 
-Will run some.test in the given tox venv.
+Will run some.test in the given nox venv.
 
 Both modes can be run with no parameters to have testtools run all the tests.

ttrun/cmd.py

@@ -16,6 +16,7 @@
 # along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
 
 import argparse
+import os
 import subprocess
 import sys
 
@@ -35,14 +36,14 @@ def main():
     args = parse_arguments()
 
     if args.environment:
-        return subprocess.call(
-            [
-                ".tox/{environment}/bin/python".format(environment=args.environment),
-                "-m",
-                "testtools.run",
-            ]
-            + args.tests
-        )
+        python_path = f".nox/{args.environment}/bin/python"
+        if not os.path.exists(python_path):
+            python_path = f".tox/{args.environment}/bin/python"
+        if not os.path.exists(python_path):
+            raise RuntimeError(
+                f"{args.environment} does not exist. Have you created it yet?"
+            )
+        return subprocess.call([python_path, "-m", "testtools.run"] + args.tests)
     else:
         return testtools.run.main([sys.argv[0]] + args.tests, sys.stdout)