87 rewrap 404 errors from pypiorg (#89)

* Rewrap 404 errors from pypi.org

Fixes #87

* changelog

* cleanup

README.rst

@@ -254,6 +254,10 @@ Version History
 
 next
 
+  * In Python 3, if the package can't be found you get a more explicit exception
+    pointing out which package (URL) that failed.
+    See https://github.com/peterbe/hashin/issues/87
+
   * New flag ``--update-all`` (alias ``-u``) will parse the requirements file,
     ignore the version, and update all packages that have new versions.
     See https://github.com/peterbe/hashin/pull/88

hashin.py

@@ -20,6 +20,7 @@
 
 if sys.version_info >= (3,):
     from urllib.request import urlopen
+    from urllib.error import HTTPError
 else:
     from urllib import urlopen
 
@@ -99,12 +100,23 @@ class NoVersionsError(Exception):
     """When there are no valid versions found."""
 
 
+class PackageNotFoundError(Exception):
+    """When the package can't be found on pypi.org."""
+
+
 def _verbose(*args):
     print("* " + " ".join(args))
 
 
 def _download(url, binary=False):
-    r = urlopen(url)
+    try:
+        r = urlopen(url)
+    except HTTPError as exception:
+        status_code = exception.getcode()
+        if status_code == 404:
+            raise PackageNotFoundError(url)
+        raise PackageError("Download error. {0} on {1}".format(status_code, url))
+
     # Note that urlopen will, by default, follow redirects.
     status_code = r.getcode()
 
@@ -115,8 +127,10 @@ def _download(url, binary=False):
                 "No 'Location' header on {0} ({1})".format(url, status_code)
             )
         return _download(location)
+    elif status_code == 404:
+        raise PackageNotFoundError(url)
     elif status_code != 200:
-        raise PackageError("Package not found. {0} on {1}".format(status_code, url))
+        raise PackageError("Download error. {0} on {1}".format(status_code, url))
     if binary:
         return r.read()
     _, params = cgi.parse_header(r.headers.get("Content-Type", ""))

tests/test_cli.py

@@ -17,12 +17,15 @@
 if sys.version_info >= (3,):
     # As in, Python 3
     from io import StringIO
+    from urllib.error import HTTPError
 
     STR_TYPE = str
 else:  # Python 2
     from StringIO import StringIO
 
     FileNotFoundError = IOError  # ugly but necessary
+    # Python 2 does not have this exception.
+    HTTPError = None
 
 
 @contextmanager
@@ -1282,6 +1285,39 @@ def mocked_get(url, **options):
 
         self.assertEqual(result, expected)
 
+    @cleanup_tmpdir("hashin*")
+    @mock.patch("hashin.urlopen")
+    def test_get_package_hashes_package_not_found(self, murlopen):
+        def mocked_get(url, **options):
+            if url == "https://pypi.org/pypi/gobblygook/json":
+                if HTTPError:
+                    raise HTTPError(url, 404, "Page not found", {}, None)
+                else:
+                    return _Response({}, status_code=404)
+
+            if url == "https://pypi.org/pypi/troublemaker/json":
+                if HTTPError:
+                    raise HTTPError(url, 500, "Something went wrong", {}, None)
+                else:
+                    return _Response({}, status_code=500)
+
+            raise NotImplementedError(url)
+
+        murlopen.side_effect = mocked_get
+
+        with self.assertRaises(hashin.PackageNotFoundError) as cm:
+            hashin.get_package_hashes(
+                package="gobblygook", version="0.10", algorithm="sha256"
+            )
+        exception = cm.exception
+        self.assertEqual(str(exception), "https://pypi.org/pypi/gobblygook/json")
+
+        # Errors left as is if not a 404
+        with self.assertRaises(hashin.PackageError):
+            hashin.get_package_hashes(
+                package="troublemaker", version="0.10", algorithm="sha256"
+            )
+
     @cleanup_tmpdir("hashin*")
     @mock.patch("hashin.urlopen")
     def test_get_package_hashes_unknown_algorithm(self, murlopen):