Add test for package readme syntax errors

Fixes #445

dev-requirements.txt

@@ -8,3 +8,4 @@ sphinx-rtd-theme~=0.4
 sphinx-autodoc-typehints~=1.10.2
 pytest!=5.2.3
 pytest-cov>=2.8
+readme-renderer==24.0

scripts/eachdist.py

@@ -482,6 +482,12 @@ def lint_args(args):
             args, ("exec", "pylint {}", "--all", "--mode", "lintroots")
         )
     )
+    execute_args(
+        parse_subargs(
+            args,
+            ("exec", "python tests/check_for_valid_readme.py {}", "--all",),
+        )
+    )
 
 
 def test_args(args):

tests/check_for_valid_readme.py

@@ -0,0 +1,52 @@
+"""Test script to check README.rst files for syntax errors."""
+import argparse
+import sys
+from pathlib import Path
+
+import readme_renderer.rst
+
+
+def is_valid_rst(path):
+    """Checks if RST can be rendered on PyPI."""
+    with open(path) as f:
+        markup = f.read()
+    if readme_renderer.rst.render(markup) is None:
+        return False
+    return True
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(
+        description="Checks README.rst file in path for syntax errors."
+    )
+    parser.add_argument(
+        "paths", nargs="+", help="paths containing a README.rst to test"
+    )
+    parser.add_argument("-v", "--verbose", action="store_true")
+    return parser.parse_args()
+
+
+if __name__ == "__main__":
+    args = parse_args()
+
+    error = False
+    all_readmes_found = True
+
+    for path in [Path(path) for path in args.paths]:
+        readme = path / "README.rst"
+        if not readme.exists():
+            all_readmes_found = False
+            print("✗ No README.rst in", str(path))
+            continue
+        if not is_valid_rst(readme):
+            error = True
+            print("✗ RST syntax errors in", readme)
+            continue
+        if args.verbose:
+            print("✓", readme)
+
+    if error:
+        sys.exit(1)
+    if all_readmes_found:
+        print("All clear.")
+    print("No errors found but not all packages have a README.rst")