fix test_conda_downgrade by installing cph in test prefix

tests/test_create.py

@@ -2563,25 +2563,23 @@ def test_conda_downgrade(self):
         }, stack_callback=conda_tests_ctxt_mgmt_def_pol):
             # py_ver = str(sys.version_info[0])
             py_ver = "3"
-            with make_temp_env("conda=4.5.12", "python=" + py_ver, use_restricted_unicode=True,
+            with make_temp_env("conda=4.5.12", "conda-package-handling", "python=" + py_ver, use_restricted_unicode=True,
                                name = '_' + str(uuid4())[:8]) as prefix:  # rev 0
                 # See comment in test_init_dev_and_NoBaseEnvironmentError.
-                python_exe = join(prefix, 'python.exe') if on_win else join(prefix, 'bin', 'python')
                 conda_exe = join(prefix, 'Scripts', 'conda.exe') if on_win else join(prefix, 'bin', 'conda')
-                py_co = [python_exe, "-m", "conda"]
                 assert package_is_installed(prefix, "conda=4.5.12")
 
                 # runs our current version of conda to install into the foreign env
                 run_command(Commands.INSTALL, prefix, "lockfile")  # rev 1
                 assert package_is_installed(prefix, "lockfile")
 
                 # runs the conda in the env to install something new into the env
-                subprocess_call(py_co + ["install", "-yp", prefix, "itsdangerous"], path=prefix)  # rev 2
+                run_command(Commands.RUN, prefix, conda_exe, "install", "-yp", prefix, "itsdangerous")  #rev 2
                 PrefixData._cache_.clear()
                 assert package_is_installed(prefix, "itsdangerous")
 
                 # downgrade the version of conda in the env
-                subprocess_call_with_clean_env(py_co + ["install", "-yp", prefix, "conda=4.5.11"], path=prefix)  # rev 3
+                run_command(Commands.RUN, prefix, conda_exe, "install", "-yp", prefix, "conda=4.5.11")  # rev 3
                 PrefixData._cache_.clear()
                 assert not package_is_installed(prefix, "conda=4.5.12")
 
@@ -2596,14 +2594,14 @@ def test_conda_downgrade(self):
                 assert package_is_installed(prefix, "conda=4.5.12")
 
                 # use the conda in the env to revert to a previous state
-                subprocess_call_with_clean_env(py_co + ["install", "-yp", prefix, "--rev", "1"], path=prefix)
+                subprocess_call_with_clean_env([conda_exe, "install", "-yp", prefix, "--rev", "1"], path=prefix)
                 PrefixData._cache_.clear()
                 assert not package_is_installed(prefix, "itsdangerous")
                 PrefixData._cache_.clear()
                 assert package_is_installed(prefix, "conda=4.5.12")
                 assert package_is_installed(prefix, "python=" + py_ver)
 
-                result = subprocess_call_with_clean_env(py_co + ["info", "--json"])
+                result = subprocess_call_with_clean_env([conda_exe, "info", "--json"])
                 conda_info = json.loads(result.stdout)
                 assert conda_info["conda_version"] == "4.5.12"