Gracefully handle HTTP errors from pastebin

We find that the --pastebin option to pytest sometimes fails with "HTTP
Error 400: Bad Request". We're still investigating the exact cause of
these errors, but in the meantime, a failure to upload to the pastebin
service should probably not crash pytest and cause a test failure in the
continuous-integration.

This patch catches exceptions like HTTPError that may be thrown while
trying to communicate with the pastebin service, and reports them as a
"bad response", without crashing with a backtrace or failing the entire
test suite.

AUTHORS

@@ -173,6 +173,7 @@ mbyt
 Michael Aquilina
 Michael Birtwell
 Michael Droettboom
+Michael Goerz
 Michael Seifert
 Michal Wajszczuk
 Mihai Capotă

changelog/5764.feature.rst

@@ -0,0 +1 @@
+New behavior of the ``--pastebin`` option: failures to connect to the pastebin server are reported, without failing the pytest run

src/_pytest/pastebin.py

@@ -59,20 +59,25 @@ def create_new_paste(contents):
     Creates a new paste using bpaste.net service.
 
     :contents: paste contents as utf-8 encoded bytes
-    :returns: url to the pasted contents
+    :returns: url to the pasted contents or error message
     """
     import re
     from urllib.request import urlopen
     from urllib.parse import urlencode
 
     params = {"code": contents, "lexer": "python3", "expiry": "1week"}
     url = "https://bpaste.net"
-    response = urlopen(url, data=urlencode(params).encode("ascii")).read()
-    m = re.search(r'href="/raw/(\w+)"', response.decode("utf-8"))
+    try:
+        response = (
+            urlopen(url, data=urlencode(params).encode("ascii")).read().decode("utf-8")
+        )
+    except OSError as exc_info:  # urllib errors
+        return "bad response: %s" % exc_info
+    m = re.search(r'href="/raw/(\w+)"', response)
     if m:
         return "{}/show/{}".format(url, m.group(1))
     else:
-        return "bad response: " + response.decode("utf-8")
+        return "bad response: invalid format ('" + response + "')"
 
 
 def pytest_terminal_summary(terminalreporter):

testing/test_pastebin.py

@@ -82,6 +82,47 @@ class TestPaste:
     def pastebin(self, request):
         return request.config.pluginmanager.getplugin("pastebin")
 
+    @pytest.fixture
+    def mocked_urlopen_fail(self, monkeypatch):
+        """
+        monkeypatch the actual urlopen call to emulate a HTTP Error 400
+        """
+        calls = []
+
+        import urllib.error
+        import urllib.request
+
+        def mocked(url, data):
+            calls.append((url, data))
+            raise urllib.error.HTTPError(url, 400, "Bad request", None, None)
+
+        monkeypatch.setattr(urllib.request, "urlopen", mocked)
+        return calls
+
+    @pytest.fixture
+    def mocked_urlopen_invalid(self, monkeypatch):
+        """
+        monkeypatch the actual urlopen calls done by the internal plugin
+        function that connects to bpaste service, but return a url in an
+        unexpected format
+        """
+        calls = []
+
+        def mocked(url, data):
+            calls.append((url, data))
+
+            class DummyFile:
+                def read(self):
+                    # part of html of a normal response
+                    return b'View <a href="/invalid/3c0c6750bd">raw</a>.'
+
+            return DummyFile()
+
+        import urllib.request
+
+        monkeypatch.setattr(urllib.request, "urlopen", mocked)
+        return calls
+
     @pytest.fixture
     def mocked_urlopen(self, monkeypatch):
         """
@@ -105,6 +146,19 @@ def read(self):
         monkeypatch.setattr(urllib.request, "urlopen", mocked)
         return calls
 
+    def test_pastebin_invalid_url(self, pastebin, mocked_urlopen_invalid):
+        result = pastebin.create_new_paste(b"full-paste-contents")
+        assert (
+            result
+            == "bad response: invalid format ('View <a href=\"/invalid/3c0c6750bd\">raw</a>.')"
+        )
+        assert len(mocked_urlopen_invalid) == 1
+
+    def test_pastebin_http_error(self, pastebin, mocked_urlopen_fail):
+        result = pastebin.create_new_paste(b"full-paste-contents")
+        assert result == "bad response: HTTP Error 400: Bad request"
+        assert len(mocked_urlopen_fail) == 1
+
     def test_create_new_paste(self, pastebin, mocked_urlopen):
         result = pastebin.create_new_paste(b"full-paste-contents")
         assert result == "https://bpaste.net/show/3c0c6750bd"
@@ -127,4 +181,4 @@ def response(url, data):
 
         monkeypatch.setattr(urllib.request, "urlopen", response)
         result = pastebin.create_new_paste(b"full-paste-contents")
-        assert result == "bad response: something bad occurred"
+        assert result == "bad response: invalid format ('something bad occurred')"