From 457cf31da61a2ca3fbe7c91e11b23adb25d2c2b9 Mon Sep 17 00:00:00 2001
From: Marc Abramowitz <marc@marc-abramowitz.com>
Date: Thu, 19 Mar 2015 09:48:18 -0700
Subject: DistributionNotFound: Show requirers

It is very helpful to know who required the missing package. E.g.:

    pkg_resources.DistributionNotFound: The 'colorama>=0.3.1' distribution was not found and is required by smlib.log.

Note that there was a comment: "unfortunately, zc.buildout uses a str(err) to
get the name of the distribution here..", but I did a search in the `buildout`
code and I think that is no longer true, so I think that we're free to make the
exception message more helpful without risk of breaking buildout:

    # In clone from https://github.com/buildout/buildout
    $ ag DistributionNotFound
    src/zc/buildout/buildout.py
    686:        except (ImportError, pkg_resources.DistributionNotFound):

    $ pip install --download=. --no-install zc.buildout
    ...
      Saved ./zc.buildout-2.3.1.tar.gz
    ...
    $ tar xf zc.buildout-2.3.1.tar.gz
    $ ag DistributionNotFound zc.buildout-2.3.1
    zc.buildout-2.3.1/src/zc/buildout/buildout.py
    686:        except (ImportError, pkg_resources.DistributionNotFound):
---
 pkg_resources/__init__.py | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/pkg_resources/__init__.py b/pkg_resources/__init__.py
index c3686f88..4e820c09 100644
--- a/pkg_resources/__init__.py
+++ b/pkg_resources/__init__.py
@@ -798,13 +798,16 @@ class WorkingSet(object):
                             ws = WorkingSet([])
                     dist = best[req.key] = env.best_match(req, ws, installer)
                     if dist is None:
-                        #msg = ("The '%s' distribution was not found on this "
-                        #       "system, and is required by this application.")
-                        #raise DistributionNotFound(msg % req)
-
-                        # unfortunately, zc.buildout uses a str(err)
-                        # to get the name of the distribution here..
-                        raise DistributionNotFound(req)
+                        requirers = required_by.get(req, None)
+                        if requirers:
+                            requirers_str = ', '.join(requirers)
+                        else:
+                            requirers_str = 'this application'
+                        msg = ("The '%s' distribution was not found "
+                               "and is required by %s."
+                               % (req, requirers_str))
+                        warnings.warn(msg)
+                        raise DistributionNotFound(msg)
                 to_activate.append(dist)
             if dist not in req:
                 # Oops, the "best" so far conflicts with a dependency
-- 
cgit v1.2.1


From b24eb2cc8b7d95d39997e3b79c94544fcf7cefeb Mon Sep 17 00:00:00 2001
From: Marc Abramowitz <marc@marc-abramowitz.com>
Date: Tue, 24 Mar 2015 08:20:42 -0700
Subject: DistributionNotFound: Move message template to class

---
 pkg_resources/__init__.py          | 34 +++++++++++++++++++++++++---------
 setuptools/command/easy_install.py |  4 +---
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/pkg_resources/__init__.py b/pkg_resources/__init__.py
index 4e820c09..6f1ab9b7 100644
--- a/pkg_resources/__init__.py
+++ b/pkg_resources/__init__.py
@@ -368,6 +368,30 @@ class ContextualVersionConflict(VersionConflict):
 class DistributionNotFound(ResolutionError):
     """A requested distribution was not found"""
 
+    _template = ("The '{self.req}' distribution was not found "
+                 "and is required by {self.requirers_str}")
+
+    @property
+    def req(self):
+        return self.args[0]
+
+    @property
+    def requirers(self):
+        return self.args[1]
+
+    @property
+    def requirers_str(self):
+        if not self.requirers:
+            return 'the application'
+        return ', '.join(self.requirers)
+
+    def report(self):
+        return self._template.format(**locals())
+
+    def __str__(self):
+        return self.report()
+
+
 class UnknownExtra(ResolutionError):
     """Distribution doesn't have an "extra feature" of the given name"""
 _provider_factories = {}
@@ -799,15 +823,7 @@ class WorkingSet(object):
                     dist = best[req.key] = env.best_match(req, ws, installer)
                     if dist is None:
                         requirers = required_by.get(req, None)
-                        if requirers:
-                            requirers_str = ', '.join(requirers)
-                        else:
-                            requirers_str = 'this application'
-                        msg = ("The '%s' distribution was not found "
-                               "and is required by %s."
-                               % (req, requirers_str))
-                        warnings.warn(msg)
-                        raise DistributionNotFound(msg)
+                        raise DistributionNotFound(req, requirers)
                 to_activate.append(dist)
             if dist not in req:
                 # Oops, the "best" so far conflicts with a dependency
diff --git a/setuptools/command/easy_install.py b/setuptools/command/easy_install.py
index 276b6f99..f2bfa68d 100755
--- a/setuptools/command/easy_install.py
+++ b/setuptools/command/easy_install.py
@@ -709,9 +709,7 @@ class easy_install(Command):
                 [requirement], self.local_index, self.easy_install
             )
         except DistributionNotFound as e:
-            raise DistutilsError(
-                "Could not find required distribution %s" % e.args
-            )
+            raise DistutilsError(str(e))
         except VersionConflict as e:
             raise DistutilsError(e.report())
         if self.always_copy or self.always_copy_from:
-- 
cgit v1.2.1