ensure base directory is correctly chosen when determing best python

src/appenv.py

@@ -175,7 +175,9 @@ def ensure_minimal_python():
         sys.exit(66)
 
 
-def ensure_best_python():
+def ensure_best_python(base):
+    os.chdir(base)
+
     if "APPENV_BEST_PYTHON" in os.environ:
         # Don't do this twice to avoid being surprised with
         # accidental infinite loops.
@@ -473,7 +475,9 @@ def update_lockfile(self, args=None, remaining=None):
 
 
 def main():
-    ensure_best_python()
+    base = os.path.dirname(__file__)
+
+    ensure_best_python(base)
     # clear PYTHONPATH variable to get a defined environment
     # XXX this is a bit of history. not sure whether its still needed. keeping
     # it for good measure
@@ -482,7 +486,6 @@ def main():
 
     # Determine whether we're being called as appenv or as an application name
     application_name = os.path.splitext(os.path.basename(__file__))[0]
-    base = os.path.dirname(__file__)
 
     appenv = AppEnv(base)
     try: