tests-httpd: basic infra to run curl against an apache httpd plus nghttpx for h3

- adding '--with-test-httpd=<path>' to configure non-standard apache2
  install
- python env and base classes for running httpd
- basic tests for connectivity with h1/h2/h3
- adding test cases for truncated responses in http versions.
- adding goaway test for HTTP/3.
- adding "stuttering" tests with parallel downloads in chunks with
  varying delays between chunks.

- adding a curltest module to the httpd server, adding GOAWAY test.
    - mod_curltest now installs 2 handlers
      - 'echo': writing as response body what came as request body
      - 'tweak': with query parameters to tweak response behaviour
- marked known fails as skip for now

Closes #10175

tests/tests-httpd/test_05_errors.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+#***************************************************************************
+#                                  _   _ ____  _
+#  Project                     ___| | | |  _ \| |
+#                             / __| | | | |_) | |
+#                            | (__| |_| |  _ <| |___
+#                             \___|\___/|_| \_\_____|
+#
+# Copyright (C) 2008 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
+#
+# This software is licensed as described in the file COPYING, which
+# you should have received as part of this distribution. The terms
+# are also available at https://curl.se/docs/copyright.html.
+#
+# You may opt to use, copy, modify, merge, publish, distribute and/or sell
+# copies of the Software, and permit persons to whom the Software is
+# furnished to do so, under the terms of the COPYING file.
+#
+# This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+# KIND, either express or implied.
+#
+# SPDX-License-Identifier: curl
+#
+###########################################################################
+#
+import json
+import logging
+from typing import Optional, Tuple, List, Dict
+import pytest
+
+from testenv import Env, CurlClient, ExecResult
+
+
+log = logging.getLogger(__name__)
+
+
+@pytest.mark.skipif(condition=Env.setup_incomplete(),
+                    reason=f"missing: {Env.incomplete_reason()}")
+class TestErrors:
+
+    # download 1 file, check that we get CURLE_PARTIAL_FILE
+    @pytest.mark.parametrize("proto", ['http/1.1', 'h2', 'h3'])
+    def test_05_01_partial_1(self, env: Env, httpd, nghttpx, repeat,
+                              proto):
+        if proto == 'h3' and not env.have_h3():
+            pytest.skip("h3 not supported")
+        if proto == 'h2':  # TODO, fix error code in curl
+            pytest.skip("h2 reports exitcode 16(CURLE_HTTP2)")
+        if proto == 'h3':  # TODO, fix error code in curl
+            pytest.skip("h3 reports exitcode 95(CURLE_HTTP3)")
+        count = 1
+        curl = CurlClient(env=env)
+        urln = f'https://{env.authority_for(env.domain1, proto)}' \
+               f'/curltest/tweak?id=[0-{count - 1}]'\
+               '&chunks=3&chunk_size=16000&body_error=reset'
+        r = curl.http_download(urls=[urln], alpn_proto=proto)
+        assert r.exit_code != 0, f'{r}'
+        invalid_stats = []
+        for idx, s in enumerate(r.stats):
+            if 'exitcode' not in s or s['exitcode'] != 18:
+                invalid_stats.append(f'request {idx} exit with {s["exitcode"]}')
+        assert len(invalid_stats) == 0, f'failed: {invalid_stats}'
+
+    # download 20 file, check that we get CURLE_PARTIAL_FILE for all
+    @pytest.mark.parametrize("proto", ['h2', 'h3'])
+    def test_05_02_partial_20(self, env: Env, httpd, nghttpx, repeat,
+                              proto):
+        if proto == 'h3' and not env.have_h3():
+            pytest.skip("h3 not supported")
+        if proto == 'h2':  # TODO, fix error code in curl
+            pytest.skip("h2 reports exitcode 16(CURLE_HTTP2)")
+        if proto == 'h3':  # TODO, fix error code in curl
+            pytest.skip("h3 reports exitcode 95(CURLE_HTTP3) and takes a long time")
+        count = 20
+        curl = CurlClient(env=env)
+        urln = f'https://{env.authority_for(env.domain1, proto)}' \
+               f'/curltest/tweak?id=[0-{count - 1}]'\
+               '&chunks=3&chunk_size=16000&body_error=reset'
+        r = curl.http_download(urls=[urln], alpn_proto=proto)
+        assert r.exit_code != 0, f'{r}'
+        assert len(r.stats) == count, f'did not get all stats: {r}'
+        invalid_stats = []
+        for idx, s in enumerate(r.stats):
+            if 'exitcode' not in s or s['exitcode'] != 18:
+                invalid_stats.append(f'request {idx} exit with {s["exitcode"]}')
+        assert len(invalid_stats) == 0, f'failed: {invalid_stats}'