vpython: Forcefully clear PYTHON* environment.

vpython/run.go

Index: vpython/run.go
diff --git a/vpython/run.go b/vpython/run.go
index b817f1cbc46f248df972e4df3d8fa2403cd5c3db..85d42ffe97ba133d67bffe7e00c674d1d84226bf 100644
--- a/vpython/run.go
+++ b/vpython/run.go
@@ -66,6 +66,14 @@ func Run(c context.Context, opts Options) error {
 			e = environ.System()
 		}
 
+		// Remove PYTHONPATH and PYTHONHOME from the environment. This prevents them
+		// from being propagated to delegate processes (e.g., "vpython" script calls
+		// Python script, the "vpython" one uses the Interpreter's IsolatedCommand
+		// to isolate the initial run, but the delegate command blindly uses the
+		// environment that it's provided).
+		e.Remove("PYTHONPATH")
+		e.Remove("PYTHONHOME")

[iannucci, 2017/05/08 18:59:08]

what about site path stuff? or do these cover that?

[dnj, 2017/05/08 19:03:07]

Adding PYTHONNOUSERSITE, which prevents this.

+
 		e.Set("VIRTUAL_ENV", ve.Root) // Set by VirtualEnv script.
 		if ve.EnvironmentStampPath != "" {
 			e.Set(EnvironmentStampPathENV, ve.EnvironmentStampPath)