Use reliable path to python interpreter in cli test (#678)

Author: AMDmi3

test/test_wordcloud_cli.py

@@ -1,6 +1,7 @@
 import argparse
 import os
 import subprocess
+import sys
 from collections import namedtuple
 import contextlib
 
@@ -183,8 +184,8 @@ def test_cli_regexp_invalid(tmp_text_file, capsys):
 
 @pytest.mark.parametrize("command,expected_output, expected_exit_code", [
     ("wordcloud_cli --help", "usage: wordcloud_cli", 0),
-    ("python -m wordcloud --help", "usage: __main__", 0),
-    ("python %s/../wordcloud/wordcloud_cli.py --help" % os.path.dirname(__file__), "To execute the CLI", 1),
+    ("%s -m wordcloud --help" % sys.executable, "usage: __main__", 0),
+    ("%s %s/../wordcloud/wordcloud_cli.py --help" % (sys.executable, os.path.dirname(__file__)), "To execute the CLI", 1),
 ])
 def test_cli_as_executable(command, expected_output, expected_exit_code, tmpdir, capfd, no_cover_compat):