Restore Always OR interpreter constraints when given list

Per pex-tool#655 (comment), Chris is okay with always ORing. This is a much more consistent and simpler approach, so is ideal over the earlier conditional logic.

pex/interpreter_constraints.py

@@ -21,22 +21,18 @@ def validate_constraints(constraints):
       die("Compatibility requirements are not formatted properly: %s" % str(e))
 
 
-def matched_interpreters(interpreters, constraints, meet_all_constraints=False):
-  """Given some filters, yield any interpreter that matches at least one of them, or all of them
-     if meet_all_constraints is set to True.
+def matched_interpreters(interpreters, constraints):
+  """Given some filters, yield any interpreter that matches at least one of them.
 
   :param interpreters: a list of PythonInterpreter objects for filtering
   :param constraints: A sequence of strings that constrain the interpreter compatibility for this
-    pex. Each string uses the Requirement-style format, e.g. 'CPython>=3' or '>=2.7,<3' for requirements
-    agnostic to interpreter class. Multiple requirement strings may be combined into a list, such as
-    ['CPython>=2.7,<3', 'CPython>=3.4'], to either OR or AND the requirements depending on `meet_all_constraints`.
-  :param meet_all_constraints: whether to match against all filters (AND).
-    Defaults to matching interpreters that match at least one filter (OR).
+    pex. Each string uses the Requirement-style format, e.g. 'CPython>=3' or '>=2.7,<3' for
+    requirements agnostic to interpreter class. Multiple requirement strings may be combined
+    into a list to OR the constraints, such as ['CPython>=2.7,<3', 'CPython>=3.4'].
   :return interpreter: returns a generator that yields compatible interpreters
   """
-  check = all if meet_all_constraints else any
   for interpreter in interpreters:
-    if check(interpreter.identity.matches(filt) for filt in constraints):
+    if any(interpreter.identity.matches(filt) for filt in constraints):
       TRACER.log("Constraints on interpreters: %s, Matching Interpreter: %s"
                  % (constraints, interpreter.binary), V=3)
       yield interpreter

pex/pex_bootstrapper.py

@@ -89,8 +89,7 @@ def find_compatible_interpreters(pex_python_path, compatibility_constraints):
       # get all qualifying interpreters found in $PATH
       interpreters = PythonInterpreter.all()
 
-  return list(matched_interpreters(
-    interpreters, compatibility_constraints, meet_all_constraints=meet_all_constraints))
+  return list(matched_interpreters(interpreters, compatibility_constraints))
 
 
 def _select_pex_python_interpreter(target_python, compatibility_constraints):
@@ -100,8 +99,7 @@ def _select_pex_python_interpreter(target_python, compatibility_constraints):
     die('Failed to find interpreter specified by PEX_PYTHON: %s' % target)
   if compatibility_constraints:
     pi = PythonInterpreter.from_binary(target)
-    # AND the interpreter constraints
-    if not list(matched_interpreters([pi], compatibility_constraints, meet_all_constraints=True)):
+    if not list(matched_interpreters([pi], compatibility_constraints)):
       die('Interpreter specified by PEX_PYTHON (%s) is not compatible with specified '
           'interpreter constraints: %s' % (target, str(compatibility_constraints)))
   if not os.path.exists(target):