--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/planemo/lib/python3.7/site-packages/distlib/markers.py	Fri Jul 31 00:18:57 2020 -0400
@@ -0,0 +1,131 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2012-2017 Vinay Sajip.
+# Licensed to the Python Software Foundation under a contributor agreement.
+# See LICENSE.txt and CONTRIBUTORS.txt.
+#
+"""
+Parser for the environment markers micro-language defined in PEP 508.
+"""
+
+# Note: In PEP 345, the micro-language was Python compatible, so the ast
+# module could be used to parse it. However, PEP 508 introduced operators such
+# as ~= and === which aren't in Python, necessitating a different approach.
+
+import os
+import sys
+import platform
+import re
+
+from .compat import python_implementation, urlparse, string_types
+from .util import in_venv, parse_marker
+
+__all__ = ['interpret']
+
+def _is_literal(o):
+    if not isinstance(o, string_types) or not o:
+        return False
+    return o[0] in '\'"'
+
+class Evaluator(object):
+    """
+    This class is used to evaluate marker expessions.
+    """
+
+    operations = {
+        '==': lambda x, y: x == y,
+        '===': lambda x, y: x == y,
+        '~=': lambda x, y: x == y or x > y,
+        '!=': lambda x, y: x != y,
+        '<':  lambda x, y: x < y,
+        '<=':  lambda x, y: x == y or x < y,
+        '>':  lambda x, y: x > y,
+        '>=':  lambda x, y: x == y or x > y,
+        'and': lambda x, y: x and y,
+        'or': lambda x, y: x or y,
+        'in': lambda x, y: x in y,
+        'not in': lambda x, y: x not in y,
+    }
+
+    def evaluate(self, expr, context):
+        """
+        Evaluate a marker expression returned by the :func:`parse_requirement`
+        function in the specified context.
+        """
+        if isinstance(expr, string_types):
+            if expr[0] in '\'"':
+                result = expr[1:-1]
+            else:
+                if expr not in context:
+                    raise SyntaxError('unknown variable: %s' % expr)
+                result = context[expr]
+        else:
+            assert isinstance(expr, dict)
+            op = expr['op']
+            if op not in self.operations:
+                raise NotImplementedError('op not implemented: %s' % op)
+            elhs = expr['lhs']
+            erhs = expr['rhs']
+            if _is_literal(expr['lhs']) and _is_literal(expr['rhs']):
+                raise SyntaxError('invalid comparison: %s %s %s' % (elhs, op, erhs))
+
+            lhs = self.evaluate(elhs, context)
+            rhs = self.evaluate(erhs, context)
+            result = self.operations[op](lhs, rhs)
+        return result
+
+def default_context():
+    def format_full_version(info):
+        version = '%s.%s.%s' % (info.major, info.minor, info.micro)
+        kind = info.releaselevel
+        if kind != 'final':
+            version += kind[0] + str(info.serial)
+        return version
+
+    if hasattr(sys, 'implementation'):
+        implementation_version = format_full_version(sys.implementation.version)
+        implementation_name = sys.implementation.name
+    else:
+        implementation_version = '0'
+        implementation_name = ''
+
+    result = {
+        'implementation_name': implementation_name,
+        'implementation_version': implementation_version,
+        'os_name': os.name,
+        'platform_machine': platform.machine(),
+        'platform_python_implementation': platform.python_implementation(),
+        'platform_release': platform.release(),
+        'platform_system': platform.system(),
+        'platform_version': platform.version(),
+        'platform_in_venv': str(in_venv()),
+        'python_full_version': platform.python_version(),
+        'python_version': platform.python_version()[:3],
+        'sys_platform': sys.platform,
+    }
+    return result
+
+DEFAULT_CONTEXT = default_context()
+del default_context
+
+evaluator = Evaluator()
+
+def interpret(marker, execution_context=None):
+    """
+    Interpret a marker and return a result depending on environment.
+
+    :param marker: The marker to interpret.
+    :type marker: str
+    :param execution_context: The context used for name lookup.
+    :type execution_context: mapping
+    """
+    try:
+        expr, rest = parse_marker(marker)
+    except Exception as e:
+        raise SyntaxError('Unable to interpret marker syntax: %s: %s' % (marker, e))
+    if rest and rest[0] != '#':
+        raise SyntaxError('unexpected trailing data in marker: %s: %s' % (marker, rest))
+    context = dict(DEFAULT_CONTEXT)
+    if execution_context:
+        context.update(execution_context)
+    return evaluator.evaluate(expr, context)