Rewrite making test certificates (#393)

Also updates obsolete curl dependencies with zlib.

tests/check_cryptography.py

@@ -0,0 +1,40 @@
+#!/usr/bin/python3
+"""Check cryptography module."""
+
+import sys
+
+try:
+    import cryptography
+    print(cryptography.__version__, end="")
+except ModuleNotFoundError as ierr:
+    print("Module not installed: {}".format(ierr))
+    sys.exit(1)
+except ImportError as ierr:
+    print("Module not found: {}".format(ierr))
+    sys.exit(1)
+
+class UnsupportedVersion(Exception):
+    """Unsupported version"""
+
+def main() -> None:
+    """Check python3-cryptography version"""
+    try:
+        version = tuple(int(num) for num in cryptography.__version__.split('.'))
+        if version < (37, 0, 2):
+            raise UnsupportedVersion("unsupported python3-cryptography version")
+    except UnsupportedVersion as err:
+        print(" {}".format(err), end="")
+        sys.exit(1)
+
+
+if __name__ == '__main__':
+    main()
+
+# pylint: disable=pointless-string-statement
+"""Local Variables:
+    c-basic-offset: 4
+    tab-width: 4
+    indent-tabs-mode: nil
+End:
+    vim: set ts=4 expandtab:
+"""