Allow the use of many sources instead of just 2

- Fixes #2130

Signed-off-by: Dan Ryan <dan@danryan.co>

tests/integration/test_project.py

@@ -111,3 +111,35 @@ def test_maintain_file_line_endings(PipenvInstance, pypi, newlines):
                 actual_newlines, newlines, fn,
             )
             # message because of  https://github.com/pytest-dev/pytest/issues/3443
+
+
+@pytest.mark.project
+@pytest.mark.sources
+def test_many_indexes(PipenvInstance, pypi):
+    with PipenvInstance(pypi=pypi, chdir=True) as p:
+        with open(p.pipfile_path, 'w') as f:
+            contents = """
+[[source]]
+url = "{0}"
+verify_ssl = false
+name = "testindex"
+
+[[source]]
+url = "https://pypi.org/simple"
+verify_ssl = "true"
+name = "pypi"
+
+[[source]]
+url = "https://pypi.python.org/simple"
+verify_ssl = "true"
+name = "legacy"
+
+[packages]
+pytz = "*"
+six = {{version = "*", index = "pypi"}}
+
+[dev-packages]
+            """.format(os.environ['PIPENV_TEST_INDEX']).strip()
+            f.write(contents)
+        c = p.pipenv('install')
+        assert c.return_code == 0