--- a/testing/mozharness/mozharness/base/python.py
+++ b/testing/mozharness/mozharness/base/python.py
@@ -108,43 +108,44 @@ class VirtualenvMixin(object):
 
         See the documentation for install_module for how the arguments are
         applied.
         """
         self._virtualenv_modules.append((name, url, method, requirements,
                                          optional, two_pass, editable))
 
     def query_virtualenv_path(self):
-        c = self.config
+        """Determine the absolute path to the virtualenv."""
         dirs = self.query_abs_dirs()
-        virtualenv = None
+
         if 'abs_virtualenv_dir' in dirs:
-            virtualenv = dirs['abs_virtualenv_dir']
-        elif c.get('virtualenv_path'):
-            if os.path.isabs(c['virtualenv_path']):
-                virtualenv = c['virtualenv_path']
-            else:
-                virtualenv = os.path.join(dirs['abs_work_dir'],
-                                          c['virtualenv_path'])
-        return virtualenv
+            return dirs['abs_virtualenv_dir']
+
+        p = self.config['virtualenv_path']
+        if not p:
+            self.fatal('virtualenv_path config option not set; '
+                       'this should never happen')
+
+        if os.path.isabs(p):
+            return p
+        else:
+            return os.path.join(dirs['abs_work_dir'], p)
 
     def query_python_path(self, binary="python"):
         """Return the path of a binary inside the virtualenv, if
         c['virtualenv_path'] is set; otherwise return the binary name.
         Otherwise return None
         """
         if binary not in self.python_paths:
             bin_dir = 'bin'
             if self._is_windows():
                 bin_dir = 'Scripts'
             virtualenv_path = self.query_virtualenv_path()
-            if virtualenv_path:
-                self.python_paths[binary] = os.path.abspath(os.path.join(virtualenv_path, bin_dir, binary))
-            else:
-                self.python_paths[binary] = self.query_exe(binary)
+            self.python_paths[binary] = os.path.abspath(os.path.join(virtualenv_path, bin_dir, binary))
+
         return self.python_paths[binary]
 
     def query_python_site_packages_path(self):
         if self.site_packages_path:
             return self.site_packages_path
         python = self.query_python_path()
         self.site_packages_path = self.get_output_from_command(
             [python, '-c',