diff --git a/news/5188.bugfix b/news/5188.bugfix
new file mode 100644
index 00000000000..27325639e88
--- /dev/null
+++ b/news/5188.bugfix
@@ -0,0 +1 @@
+Fix PEP 518 support.
diff --git a/src/pip/_internal/build_env.py b/src/pip/_internal/build_env.py
index 04e1861ebb0..791d7346588 100644
--- a/src/pip/_internal/build_env.py
+++ b/src/pip/_internal/build_env.py
@@ -2,6 +2,7 @@
 """
 
 import os
+from distutils.sysconfig import get_python_lib
 from sysconfig import get_paths
 
 from pip._internal.utils.temp_dir import TempDirectory
@@ -38,11 +39,14 @@ def __enter__(self):
         else:
             os.environ['PATH'] = scripts + os.pathsep + os.defpath
 
-        if install_dirs['purelib'] == install_dirs['platlib']:
-            lib_dirs = install_dirs['purelib']
+        # Note: prefer distutils' sysconfig to get the
+        # library paths so PyPy is correctly supported.
+        purelib = get_python_lib(plat_specific=0, prefix=self.path)
+        platlib = get_python_lib(plat_specific=1, prefix=self.path)
+        if purelib == platlib:
+            lib_dirs = purelib
         else:
-            lib_dirs = install_dirs['purelib'] + os.pathsep + \
-                install_dirs['platlib']
+            lib_dirs = purelib + os.pathsep + platlib
         if self.save_pythonpath:
             os.environ['PYTHONPATH'] = lib_dirs + os.pathsep + \
                 self.save_pythonpath
diff --git a/src/pip/_internal/commands/wheel.py b/src/pip/_internal/commands/wheel.py
index 8a85d873001..ac55f91e62e 100644
--- a/src/pip/_internal/commands/wheel.py
+++ b/src/pip/_internal/commands/wheel.py
@@ -11,7 +11,6 @@
 from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req import RequirementSet
 from pip._internal.resolve import Resolver
-from pip._internal.utils.misc import import_or_raise
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.wheel import WheelBuilder
 
@@ -102,28 +101,7 @@ def __init__(self, *args, **kw):
         self.parser.insert_option_group(0, index_opts)
         self.parser.insert_option_group(0, cmd_opts)
 
-    def check_required_packages(self):
-        import_or_raise(
-            'wheel.bdist_wheel',
-            CommandError,
-            "'pip wheel' requires the 'wheel' package. To fix this, run: "
-            "pip install wheel"
-        )
-
-        need_setuptools_message = (
-            "'pip wheel' requires setuptools >= 0.8 for dist-info support. "
-            "To fix this, run: pip install --upgrade setuptools>=0.8"
-        )
-        pkg_resources = import_or_raise(
-            'pkg_resources',
-            CommandError,
-            need_setuptools_message
-        )
-        if not hasattr(pkg_resources, 'DistInfoDistribution'):
-            raise CommandError(need_setuptools_message)
-
     def run(self, options, args):
-        self.check_required_packages()
         cmdoptions.check_install_build_global(options)
 
         index_urls = [options.index_url] + options.extra_index_urls
diff --git a/src/pip/_internal/operations/prepare.py b/src/pip/_internal/operations/prepare.py
index 2c4ff94cb1c..7d1297ea00b 100644
--- a/src/pip/_internal/operations/prepare.py
+++ b/src/pip/_internal/operations/prepare.py
@@ -126,25 +126,31 @@ def prep_for_dist(self, finder, build_isolation):
         build_requirements, isolate = self.req.get_pep_518_info()
         should_isolate = build_isolation and isolate
 
-        if 'setuptools' not in build_requirements:
+        minimum_requirements = ('setuptools', 'wheel')
+        missing_requirements = set(minimum_requirements) - set(
+            pkg_resources.Requirement(r).key
+            for r in build_requirements
+        )
+        if missing_requirements:
+            def format_reqs(rs):
+                return ' and '.join(map(repr, sorted(rs)))
             logger.warning(
-                "%s does not include 'setuptools' as a buildtime requirement "
-                "in its pyproject.toml.", self.req.name,
+                "Missing build time requirements in pyproject.toml for %s: "
+                "%s.", self.req, format_reqs(missing_requirements)
             )
             logger.warning(
                 "This version of pip does not implement PEP 517 so it cannot "
-                "build a wheel without setuptools."
+                "build a wheel without %s.", format_reqs(minimum_requirements)
             )
 
-        if not should_isolate:
-            self.req.build_env = NoOpBuildEnvironment(no_clean=False)
-
-        with self.req.build_env as prefix:
-            if should_isolate:
+        if should_isolate:
+            with self.req.build_env as prefix:
                 _install_build_reqs(finder, prefix, build_requirements)
+        else:
+            self.req.build_env = NoOpBuildEnvironment(no_clean=False)
 
-            self.req.run_egg_info()
-            self.req.assert_source_matches_version()
+        self.req.run_egg_info()
+        self.req.assert_source_matches_version()
 
 
 class Installed(DistAbstraction):
diff --git a/src/pip/_internal/req/req_install.py b/src/pip/_internal/req/req_install.py
index 04bb3fd65c0..ddd167c66c0 100644
--- a/src/pip/_internal/req/req_install.py
+++ b/src/pip/_internal/req/req_install.py
@@ -413,24 +413,6 @@ def setup_py_dir(self):
     @property
     def setup_py(self):
         assert self.source_dir, "No source dir for %s" % self
-        cmd = [sys.executable, '-c', 'import setuptools']
-        output = call_subprocess(
-            cmd,
-            show_stdout=False,
-            command_desc='python -c "import setuptools"',
-            on_returncode='ignore',
-        )
-
-        if output:
-            if get_installed_version('setuptools') is None:
-                add_msg = "Please install setuptools."
-            else:
-                add_msg = output
-            # Setuptools is not available
-            raise InstallationError(
-                "Could not import setuptools which is required to "
-                "install from a source distribution.\n%s" % add_msg
-            )
 
         setup_py = os.path.join(self.setup_py_dir, 'setup.py')
 
@@ -496,11 +478,12 @@ def run_egg_info(self):
                 egg_info_dir = os.path.join(self.setup_py_dir, 'pip-egg-info')
                 ensure_dir(egg_info_dir)
                 egg_base_option = ['--egg-base', 'pip-egg-info']
-            call_subprocess(
-                egg_info_cmd + egg_base_option,
-                cwd=self.setup_py_dir,
-                show_stdout=False,
-                command_desc='python setup.py egg_info')
+            with self.build_env:
+                call_subprocess(
+                    egg_info_cmd + egg_base_option,
+                    cwd=self.setup_py_dir,
+                    show_stdout=False,
+                    command_desc='python setup.py egg_info')
 
         if not self.req:
             if isinstance(parse_version(self.pkg_info()["Version"]), Version):
@@ -788,12 +771,13 @@ def install(self, install_options, global_options=None, root=None,
             msg = 'Running setup.py install for %s' % (self.name,)
             with open_spinner(msg) as spinner:
                 with indent_log():
-                    call_subprocess(
-                        install_args + install_options,
-                        cwd=self.setup_py_dir,
-                        show_stdout=False,
-                        spinner=spinner,
-                    )
+                    with self.build_env:
+                        call_subprocess(
+                            install_args + install_options,
+                            cwd=self.setup_py_dir,
+                            show_stdout=False,
+                            spinner=spinner,
+                        )
 
             if not os.path.exists(record_filename):
                 logger.debug('Record file %s not found', record_filename)
diff --git a/tests/functional/test_install.py b/tests/functional/test_install.py
index 87db792d066..f1fcf14748c 100644
--- a/tests/functional/test_install.py
+++ b/tests/functional/test_install.py
@@ -19,48 +19,30 @@
 from tests.lib.path import Path
 
 
-def test_without_setuptools(script, data):
-    script.pip("uninstall", "setuptools", "-y")
-    result = script.run(
-        "python", "-c",
-        "import pip._internal; pip._internal.main(["
-        "'install', "
-        "'INITools==0.2', "
-        "'-f', '%s', "
-        "'--no-binary=:all:'])" % data.packages,
-        expect_error=True,
-    )
-    assert (
-        "Could not import setuptools which is required to install from a "
-        "source distribution."
-        in result.stderr
-    )
-    assert "Please install setuptools" in result.stderr
-
-
-def test_with_setuptools_and_import_error(script, data):
-    # Make sure we get an ImportError while importing setuptools
-    setuptools_init_path = script.site_packages_path.join(
-        "setuptools", "__init__.py")
-    with open(setuptools_init_path, 'a') as f:
-        f.write('\nraise ImportError("toto")')
-
-    result = script.run(
-        "python", "-c",
-        "import pip._internal; pip._internal.main(["
-        "'install', "
-        "'INITools==0.2', "
-        "'-f', '%s', "
-        "'--no-binary=:all:'])" % data.packages,
-        expect_error=True,
-    )
-    assert (
-        "Could not import setuptools which is required to install from a "
-        "source distribution."
-        in result.stderr
-    )
-    assert "Traceback " in result.stderr
-    assert "ImportError: toto" in result.stderr
+@pytest.mark.parametrize('original_setuptools', ('missing', 'bad'))
+def test_pep518_uses_build_env(script, data, original_setuptools):
+    if original_setuptools == 'missing':
+        script.pip("uninstall", "-y", "setuptools")
+    elif original_setuptools == 'bad':
+        setuptools_init_path = script.site_packages_path.join(
+            "setuptools", "__init__.py")
+        with open(setuptools_init_path, 'a') as f:
+            f.write('\nraise ImportError("toto")')
+    else:
+        raise ValueError(original_setuptools)
+    to_install = data.src.join("pep518-3.0")
+    for command in ('install', 'wheel'):
+        kwargs = {}
+        if sys.version_info[:2] == (3, 3):
+            # Ignore Python 3.3 deprecation warning...
+            kwargs['expect_stderr'] = True
+        script.run(
+            "python", "-c",
+            "import pip._internal; pip._internal.main(["
+            "%r, " "'-f', %r, " "%r, "
+            "])" % (command, str(data.packages), str(to_install)),
+            **kwargs
+        )
 
 
 @pytest.mark.network
diff --git a/tests/functional/test_wheel.py b/tests/functional/test_wheel.py
index b83702599e1..68772f378fe 100644
--- a/tests/functional/test_wheel.py
+++ b/tests/functional/test_wheel.py
@@ -9,17 +9,6 @@
 from tests.lib import pyversion
 
 
-def test_basic_pip_wheel_fails_without_wheel(script, data):
-    """
-    Test 'pip wheel' fails without wheel
-    """
-    result = script.pip(
-        'wheel', '--no-index', '-f', data.find_links, 'simple==3.0',
-        expect_error=True,
-    )
-    assert "'pip wheel' requires the 'wheel' package" in result.stderr
-
-
 def test_wheel_exit_status_code_when_no_requirements(script, common_wheels):
     """
     Test wheel exit status code when no requirements specified