Remove assertion reinterpretation

The assertion reinterpretation is an old backwards compatibility
mode which was no longer being maintained on feature-parity with
the assertion rewriting mode.  It was also responsible for some
dubious patching of builtins and test with side-effects would
suddenly start passing.  Since re-writing has been the default for
a long time and plugins are now also re-written it is time to
retire reinterpretation.

_pytest/_code/__init__.py

@@ -4,9 +4,6 @@ from .code import ExceptionInfo  # noqa
 from .code import Frame  # noqa
 from .code import Traceback  # noqa
 from .code import getrawcode  # noqa
-from .code import patch_builtins  # noqa
-from .code import unpatch_builtins  # noqa
 from .source import Source  # noqa
 from .source import compile_ as compile  # noqa
 from .source import getfslineno  # noqa
-

_pytest/_code/code.py

@@ -179,18 +179,6 @@ class TracebackEntry(object):
         return self.frame.f_locals
     locals = property(getlocals, None, None, "locals of underlaying frame")
 
-    def reinterpret(self):
-        """Reinterpret the failing statement and returns a detailed information
-           about what operations are performed."""
-        from _pytest.assertion.reinterpret import reinterpret
-        if self.exprinfo is None:
-            source = py.builtin._totext(self.statement).strip()
-            x = reinterpret(source, self.frame, should_fail=True)
-            if not py.builtin._istext(x):
-                raise TypeError("interpret returned non-string %r" % (x,))
-            self.exprinfo = x
-        return self.exprinfo
-
     def getfirstlinesource(self):
         # on Jython this firstlineno can be -1 apparently
         return max(self.frame.code.firstlineno, 0)
@@ -830,29 +818,6 @@ class ReprFuncArgs(TerminalRepr):
             tw.line("")
 
 
-
-oldbuiltins = {}
-
-def patch_builtins(assertion=True, compile=True):
-    """ put compile and AssertionError builtins to Python's builtins. """
-    if assertion:
-        from _pytest.assertion import reinterpret
-        l = oldbuiltins.setdefault('AssertionError', [])
-        l.append(py.builtin.builtins.AssertionError)
-        py.builtin.builtins.AssertionError = reinterpret.AssertionError
-    if compile:
-        import _pytest._code
-        l = oldbuiltins.setdefault('compile', [])
-        l.append(py.builtin.builtins.compile)
-        py.builtin.builtins.compile = _pytest._code.compile
-
-def unpatch_builtins(assertion=True, compile=True):
-    """ remove compile and AssertionError builtins from Python builtins. """
-    if assertion:
-        py.builtin.builtins.AssertionError = oldbuiltins['AssertionError'].pop()
-    if compile:
-        py.builtin.builtins.compile = oldbuiltins['compile'].pop()
-
 def getrawcode(obj, trycall=True):
     """ return code object for given function. """
     try: