Delete cached requirements en mass

Currently we delete succesfully installed requirements and not ones
that failed. Then (most of the time) we delete the requirements cache
that contained them, deleting everything. This means that useful
debugging context is lost (when we don't delete the cache), and we've
got complexity serving no point. Instead, either keep everything or
delete it all.

pip/commands/install.py

@@ -320,12 +320,8 @@ def run(self, options, args):
                                 'Successfully downloaded %s', downloaded
                             )
                 except PreviousBuildDirError:
-                    options.no_clean = True
+                    req_cache.delete = False
                     raise
-                finally:
-                    # Clean up
-                    if not options.no_clean:
-                        requirement_set.cleanup_files()
 
         if options.target_dir:
             ensure_dir(options.target_dir)

pip/commands/wheel.py

@@ -195,8 +195,5 @@ def run(self, options, args):
                             "Failed to build one or more wheels"
                         )
                 except PreviousBuildDirError:
-                    options.no_clean = True
+                    req_cache.delete = False
                     raise
-                finally:
-                    if not options.no_clean:
-                        requirement_set.cleanup_files()

pip/req/req_cache.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 
 from collections import defaultdict
+import logging
 import os.path
 import shutil
 import tempfile
@@ -9,6 +10,9 @@
 from pip.utils import display_path, ensure_dir, rmtree, _make_build_dir
 
 
+logger = logging.getLogger(__name__)
+
+
 class RequirementCache(object):
     """A cache of requirements.
 
@@ -77,6 +81,7 @@ def __exit__(self, exc, value, tb):
 
     def cleanup(self):
         if self.delete:
+            logger.debug('Cleaning up...')
             rmtree(self.path)
         self.path = None
         self._urls = None

pip/req/req_set.py

@@ -175,7 +175,6 @@ def __init__(self, req_cache, download_dir, upgrade=False,
         self.ignore_dependencies = ignore_dependencies
         self.successfully_downloaded = []
         self.successfully_installed = []
-        self.reqs_to_cleanup = []
         self.as_egg = as_egg
         self.use_user_site = use_user_site
         self.target_dir = target_dir  # set from --target option
@@ -535,9 +534,6 @@ def add_req(subreq):
                 for subreq in dist.requires(available_requested):
                     add_req(subreq)
 
-            # cleanup tmp src
-            self.reqs_to_cleanup.append(req_to_install)
-
             if not req_to_install.editable and not req_to_install.satisfied_by:
                 # XXX: --no-install leads this to report 'Successfully
                 # downloaded' for only non-editable reqs, even though we took
@@ -546,13 +542,6 @@ def add_req(subreq):
 
         return more_reqs
 
-    def cleanup_files(self):
-        """Clean up files, remove builds."""
-        logger.debug('Cleaning up...')
-        with indent_log():
-            for req in self.reqs_to_cleanup:
-                req.remove_temporary_source()
-
     def _to_install(self):
         """Create the installation order.