preemptive conflict avoidance

tox_pyenv.py

@@ -67,7 +67,12 @@ class PyenvMissing(ToxPyenvException, RuntimeError):
     """The pyenv program is not installed."""
 
 
-class PyenvWhichFailed(ToxPyenvException):
+class PyenvFailed(ToxPyenvException):
+
+    """Calling `pyenv` failed."""
+
+
+class PyenvWhichFailed(PyenvFailed):
 
     """Calling `pyenv which` failed."""
 
@@ -173,6 +178,39 @@ def _enable_and_call(_available_version):
         return _enable_and_call(match)
 
 
+@tox_hookimpl
+def tox_get_python_executable(envconfig):
+    try:
+        pyenv = (getattr(py.path.local.sysfind('pyenv'), 'strpath', 'pyenv')
+                 or 'pyenv')
+        cmd = [pyenv, 'which', envconfig.basepython]
+        pipe = subprocess.Popen(
+            cmd,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            universal_newlines=True
+        )
+        out, err = pipe.communicate()
+    except OSError:
+        err = '\'pyenv\': command not found'
+        LOG.warning(
+            "pyenv doesn't seem to be installed, you probably "
+            "don't want this plugin installed either."
+        )
+    else:
+        if pipe.poll() == 0:
+            return out.strip()
+        else:
+            if not envconfig.tox_pyenv_fallback:
+                raise PyenvFailed(err)
+    LOG.debug("`%s` failed thru tox-pyenv plugin, falling back. "
+              "STDERR: \"%s\" | To disable this behavior, set "
+              "tox_pyenv_fallback=False in your tox.ini or use "
+              " --tox-pyenv-no-fallback on the command line.",
+              ' '.join([str(x) for x in cmd]), err)
+
+
+
 @tox_hookimpl
 def tox_get_python_executable(envconfig):
     """Hook into tox plugins to use pyenv to find executables."""