chore: Fix path to HTML coverage report during local tox run (#797)

* Fix path to HTML coverage report during local `tox` run
* Do not show how to serve coverage report if there is no coverage

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Co-authored-by: 🇺🇦 Sviatoslav Sydorenko (Святослав Сидоренко) <[email protected]>

Author: MaxymVlasov

tox.ini

@@ -91,11 +91,12 @@ commands_post =
       cov_html_reports or sys.exit(); \
       cov_html_report_dir = pathlib.Path(cov_html_reports[-1]); \
       index_file = cov_html_report_dir / "index.html";\
+      index_file.exists() or sys.exit(); \
       html_url = f"file://\{index_file\}";\
       browse_cmd = shlex.join(("python3", "-Im", "webbrowser", html_url)); \
       serve_cmd = shlex.join((\
         "python3", "-Im", "http.server", \
-        "--directory", "cov_html_report_dir", "0", \
+        "--directory", str(cov_html_report_dir), "0", \
       )); \
       print(f"\nTo open the HTML coverage report, run\n\n\
       \t\{browse_cmd !s\}\n");\