--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.7/site-packages/packaging/markers.py	Thu May 14 14:56:58 2020 -0400
@@ -0,0 +1,328 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+from __future__ import absolute_import, division, print_function
+
+import operator
+import os
+import platform
+import sys
+
+from pyparsing import ParseException, ParseResults, stringStart, stringEnd
+from pyparsing import ZeroOrMore, Group, Forward, QuotedString
+from pyparsing import Literal as L  # noqa
+
+from ._compat import string_types
+from ._typing import MYPY_CHECK_RUNNING
+from .specifiers import Specifier, InvalidSpecifier
+
+if MYPY_CHECK_RUNNING:  # pragma: no cover
+    from typing import Any, Callable, Dict, List, Optional, Tuple, Union
+
+    Operator = Callable[[str, str], bool]
+
+
+__all__ = [
+    "InvalidMarker",
+    "UndefinedComparison",
+    "UndefinedEnvironmentName",
+    "Marker",
+    "default_environment",
+]
+
+
+class InvalidMarker(ValueError):
+    """
+    An invalid marker was found, users should refer to PEP 508.
+    """
+
+
+class UndefinedComparison(ValueError):
+    """
+    An invalid operation was attempted on a value that doesn't support it.
+    """
+
+
+class UndefinedEnvironmentName(ValueError):
+    """
+    A name was attempted to be used that does not exist inside of the
+    environment.
+    """
+
+
+class Node(object):
+    def __init__(self, value):
+        # type: (Any) -> None
+        self.value = value
+
+    def __str__(self):
+        # type: () -> str
+        return str(self.value)
+
+    def __repr__(self):
+        # type: () -> str
+        return "<{0}({1!r})>".format(self.__class__.__name__, str(self))
+
+    def serialize(self):
+        # type: () -> str
+        raise NotImplementedError
+
+
+class Variable(Node):
+    def serialize(self):
+        # type: () -> str
+        return str(self)
+
+
+class Value(Node):
+    def serialize(self):
+        # type: () -> str
+        return '"{0}"'.format(self)
+
+
+class Op(Node):
+    def serialize(self):
+        # type: () -> str
+        return str(self)
+
+
+VARIABLE = (
+    L("implementation_version")
+    | L("platform_python_implementation")
+    | L("implementation_name")
+    | L("python_full_version")
+    | L("platform_release")
+    | L("platform_version")
+    | L("platform_machine")
+    | L("platform_system")
+    | L("python_version")
+    | L("sys_platform")
+    | L("os_name")
+    | L("os.name")  # PEP-345
+    | L("sys.platform")  # PEP-345
+    | L("platform.version")  # PEP-345
+    | L("platform.machine")  # PEP-345
+    | L("platform.python_implementation")  # PEP-345
+    | L("python_implementation")  # undocumented setuptools legacy
+    | L("extra")  # PEP-508
+)
+ALIASES = {
+    "os.name": "os_name",
+    "sys.platform": "sys_platform",
+    "platform.version": "platform_version",
+    "platform.machine": "platform_machine",
+    "platform.python_implementation": "platform_python_implementation",
+    "python_implementation": "platform_python_implementation",
+}
+VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))
+
+VERSION_CMP = (
+    L("===") | L("==") | L(">=") | L("<=") | L("!=") | L("~=") | L(">") | L("<")
+)
+
+MARKER_OP = VERSION_CMP | L("not in") | L("in")
+MARKER_OP.setParseAction(lambda s, l, t: Op(t[0]))
+
+MARKER_VALUE = QuotedString("'") | QuotedString('"')
+MARKER_VALUE.setParseAction(lambda s, l, t: Value(t[0]))
+
+BOOLOP = L("and") | L("or")
+
+MARKER_VAR = VARIABLE | MARKER_VALUE
+
+MARKER_ITEM = Group(MARKER_VAR + MARKER_OP + MARKER_VAR)
+MARKER_ITEM.setParseAction(lambda s, l, t: tuple(t[0]))
+
+LPAREN = L("(").suppress()
+RPAREN = L(")").suppress()
+
+MARKER_EXPR = Forward()
+MARKER_ATOM = MARKER_ITEM | Group(LPAREN + MARKER_EXPR + RPAREN)
+MARKER_EXPR << MARKER_ATOM + ZeroOrMore(BOOLOP + MARKER_EXPR)
+
+MARKER = stringStart + MARKER_EXPR + stringEnd
+
+
+def _coerce_parse_result(results):
+    # type: (Union[ParseResults, List[Any]]) -> List[Any]
+    if isinstance(results, ParseResults):
+        return [_coerce_parse_result(i) for i in results]
+    else:
+        return results
+
+
+def _format_marker(marker, first=True):
+    # type: (Union[List[str], Tuple[Node, ...], str], Optional[bool]) -> str
+
+    assert isinstance(marker, (list, tuple, string_types))
+
+    # Sometimes we have a structure like [[...]] which is a single item list
+    # where the single item is itself it's own list. In that case we want skip
+    # the rest of this function so that we don't get extraneous () on the
+    # outside.
+    if (
+        isinstance(marker, list)
+        and len(marker) == 1
+        and isinstance(marker[0], (list, tuple))
+    ):
+        return _format_marker(marker[0])
+
+    if isinstance(marker, list):
+        inner = (_format_marker(m, first=False) for m in marker)
+        if first:
+            return " ".join(inner)
+        else:
+            return "(" + " ".join(inner) + ")"
+    elif isinstance(marker, tuple):
+        return " ".join([m.serialize() for m in marker])
+    else:
+        return marker
+
+
+_operators = {
+    "in": lambda lhs, rhs: lhs in rhs,
+    "not in": lambda lhs, rhs: lhs not in rhs,
+    "<": operator.lt,
+    "<=": operator.le,
+    "==": operator.eq,
+    "!=": operator.ne,
+    ">=": operator.ge,
+    ">": operator.gt,
+}  # type: Dict[str, Operator]
+
+
+def _eval_op(lhs, op, rhs):
+    # type: (str, Op, str) -> bool
+    try:
+        spec = Specifier("".join([op.serialize(), rhs]))
+    except InvalidSpecifier:
+        pass
+    else:
+        return spec.contains(lhs)
+
+    oper = _operators.get(op.serialize())  # type: Optional[Operator]
+    if oper is None:
+        raise UndefinedComparison(
+            "Undefined {0!r} on {1!r} and {2!r}.".format(op, lhs, rhs)
+        )
+
+    return oper(lhs, rhs)
+
+
+class Undefined(object):
+    pass
+
+
+_undefined = Undefined()
+
+
+def _get_env(environment, name):
+    # type: (Dict[str, str], str) -> str
+    value = environment.get(name, _undefined)  # type: Union[str, Undefined]
+
+    if isinstance(value, Undefined):
+        raise UndefinedEnvironmentName(
+            "{0!r} does not exist in evaluation environment.".format(name)
+        )
+
+    return value
+
+
+def _evaluate_markers(markers, environment):
+    # type: (List[Any], Dict[str, str]) -> bool
+    groups = [[]]  # type: List[List[bool]]
+
+    for marker in markers:
+        assert isinstance(marker, (list, tuple, string_types))
+
+        if isinstance(marker, list):
+            groups[-1].append(_evaluate_markers(marker, environment))
+        elif isinstance(marker, tuple):
+            lhs, op, rhs = marker
+
+            if isinstance(lhs, Variable):
+                lhs_value = _get_env(environment, lhs.value)
+                rhs_value = rhs.value
+            else:
+                lhs_value = lhs.value
+                rhs_value = _get_env(environment, rhs.value)
+
+            groups[-1].append(_eval_op(lhs_value, op, rhs_value))
+        else:
+            assert marker in ["and", "or"]
+            if marker == "or":
+                groups.append([])
+
+    return any(all(item) for item in groups)
+
+
+def format_full_version(info):
+    # type: (sys._version_info) -> str
+    version = "{0.major}.{0.minor}.{0.micro}".format(info)
+    kind = info.releaselevel
+    if kind != "final":
+        version += kind[0] + str(info.serial)
+    return version
+
+
+def default_environment():
+    # type: () -> Dict[str, str]
+    if hasattr(sys, "implementation"):
+        # Ignoring the `sys.implementation` reference for type checking due to
+        # mypy not liking that the attribute doesn't exist in Python 2.7 when
+        # run with the `--py27` flag.
+        iver = format_full_version(sys.implementation.version)  # type: ignore
+        implementation_name = sys.implementation.name  # type: ignore
+    else:
+        iver = "0"
+        implementation_name = ""
+
+    return {
+        "implementation_name": implementation_name,
+        "implementation_version": iver,
+        "os_name": os.name,
+        "platform_machine": platform.machine(),
+        "platform_release": platform.release(),
+        "platform_system": platform.system(),
+        "platform_version": platform.version(),
+        "python_full_version": platform.python_version(),
+        "platform_python_implementation": platform.python_implementation(),
+        "python_version": ".".join(platform.python_version_tuple()[:2]),
+        "sys_platform": sys.platform,
+    }
+
+
+class Marker(object):
+    def __init__(self, marker):
+        # type: (str) -> None
+        try:
+            self._markers = _coerce_parse_result(MARKER.parseString(marker))
+        except ParseException as e:
+            err_str = "Invalid marker: {0!r}, parse error at {1!r}".format(
+                marker, marker[e.loc : e.loc + 8]
+            )
+            raise InvalidMarker(err_str)
+
+    def __str__(self):
+        # type: () -> str
+        return _format_marker(self._markers)
+
+    def __repr__(self):
+        # type: () -> str
+        return "<Marker({0!r})>".format(str(self))
+
+    def evaluate(self, environment=None):
+        # type: (Optional[Dict[str, str]]) -> bool
+        """Evaluate a marker.
+
+        Return the boolean from evaluating the given marker against the
+        environment. environment is an optional argument to override all or
+        part of the determined environment.
+
+        The environment is determined from the current Python process.
+        """
+        current_environment = default_environment()
+        if environment is not None:
+            current_environment.update(environment)
+
+        return _evaluate_markers(self._markers, current_environment)