Remove useless python packages from required_cap

Rename stub package required_by_mixed_cap to requires_requires_cap
Move the canonicalize_name calculation outside of a loop

src/pip/_internal/commands/show.py

@@ -68,9 +68,10 @@ def search_packages_info(query):
         logger.warning('Package(s) not found: %s', ', '.join(missing))
 
     def get_requiring_packages(package_name):
+        canonical_name = canonicalize_name(package_name)
         return [
             pkg.project_name for pkg in pkg_resources.working_set
-            if canonicalize_name(package_name) in
+            if canonical_name in
                [canonicalize_name(required.name) for required in
                 pkg.requires()]
         ]

tests/data/src/required_by_capitalized/required_by_capitalized/__init__.py

-#

tests/data/src/required_by_mixed_capitalization/required_by_mixed_capitalization/__init__.py

-#

tests/data/src/required_by_mixed_capitalization/setup.py

-from setuptools import setup
-
-setup(name='simple',
-      version='1.0',
-      install_requires=['required_by_Capitalized==1.0']
-      )

tests/data/src/requires_capitalized/requires_capitalized/__init__.py

-#

tests/data/src/required_by_capitalized/setup.py → tests/data/src/requires_requires_capitalized/setup.py

 from setuptools import setup
 
-setup(name='Required_By_Capitalized',
+setup(name='requires_requires_capitalized',
       version='1.0',
+      install_requires=['requires_Capitalized==0.1']
       )

tests/functional/test_show.py

@@ -244,17 +244,18 @@ def test_show_required_by_packages_requiring_capitalized(script, data):
     where the package has a name with a mix of
     lower and upper case letters
     """
-    required_package_path = os.path.join(data.src, 'required_by_capitalized')
+    required_package_path = os.path.join(data.src, 'requires_capitalized')
     script.pip(
         'install', '--no-index', '-f', data.find_links, required_package_path
     )
-    editable_path = os.path.join(data.src, 'required_by_mixed_capitalization')
+    editable_path = os.path.join(data.src, 'requires_requires_capitalized')
     script.pip(
         'install', '--no-index', '-f', data.find_links, editable_path
     )
 
-    result = script.pip('show', 'Required_By_Capitalized')
+    result = script.pip('show', 'Requires_Capitalized')
     lines = result.stdout.splitlines()
+    print(lines)
 
-    assert 'Name: Required-By-Capitalized' in lines
-    assert 'Required-by: simple' in lines
+    assert 'Name: Requires-Capitalized' in lines
+    assert 'Required-by: requires-requires-capitalized' in lines