remove reraise logic (#1342)

* remove reraise logic - replace with re-raising import errors in the only place it is used

* remove reraise

* remove reset call from MountainCar constructor

* further remove reraise

* remove reraise import in classic_control/rendering.py

gym/__init__.py

@@ -4,7 +4,6 @@ import sys
 import warnings
 
 from gym import error
-from gym.utils import reraise
 from gym.version import VERSION as __version__
 
 from gym.core import Env, GoalEnv, Wrapper, ObservationWrapper, ActionWrapper, RewardWrapper

gym/envs/classic_control/mountain_car.py

@@ -35,7 +35,6 @@ class MountainCarEnv(gym.Env):
         self.observation_space = spaces.Box(self.low, self.high, dtype=np.float32)
 
         self.seed()
-        self.reset()
 
     def seed(self, seed=None):
         self.np_random, seed = seeding.np_random(seed)

gym/envs/classic_control/rendering.py

@@ -11,18 +11,27 @@ if "Apple" in sys.version:
         os.environ['DYLD_FALLBACK_LIBRARY_PATH'] += ':/usr/lib'
         # (JDS 2016/04/15): avoid bug on Anaconda 2.3.0 / Yosemite
 
-from gym.utils import reraise
 from gym import error
 
 try:
     import pyglet
 except ImportError as e:
-    reraise(suffix="HINT: you can install pyglet directly via 'pip install pyglet'. But if you really just want to install all Gym dependencies and not have to think about it, 'pip install -e .[all]' or 'pip install gym[all]' will do it.")
+    raise ImportError('''
+    Cannot import pyglet.
+    HINT: you can install pyglet directly via 'pip install pyglet'.
+    But if you really just want to install all Gym dependencies and not have to think about it,
+    'pip install -e .[all]' or 'pip install gym[all]' will do it.
+    ''')
 
 try:
     from pyglet.gl import *
 except ImportError as e:
-    reraise(prefix="Error occured while running `from pyglet.gl import *`",suffix="HINT: make sure you have OpenGL install. On Ubuntu, you can run 'apt-get install python-opengl'. If you're running on a server, you may need a virtual frame buffer; something like this should work: 'xvfb-run -s \"-screen 0 1400x900x24\" python <your_script.py>'")
+    raise ImportError('''
+    Error occured while running `from pyglet.gl import *`
+    HINT: make sure you have OpenGL install. On Ubuntu, you can run 'apt-get install python-opengl'.
+    If you're running on a server, you may need a virtual frame buffer; something like this should work:
+    'xvfb-run -s \"-screen 0 1400x900x24\" python <your_script.py>'
+    ''')
 
 import math
 import numpy as np

gym/utils/__init__.py

@@ -7,4 +7,3 @@ not intended as API functions, and will not remain stable over time.
 # that verify that our dependencies are actually present.
 from .colorize import colorize
 from .ezpickle import EzPickle
-from .reraise import reraise

gym/utils/reraise.py

@@ -1,41 +0,0 @@
-import sys
-
-# We keep the actual reraising in different modules, since the
-# reraising code uses syntax mutually exclusive to Python 2/3.
-if sys.version_info[0] < 3:
-    from .reraise_impl_py2 import reraise_impl #pylint: disable=E0401
-else:
-    from .reraise_impl_py3 import reraise_impl
-
-def reraise(prefix=None, suffix=None):
-    old_exc_type, old_exc_value, traceback = sys.exc_info()
-    if old_exc_value is None:
-        old_exc_value = old_exc_type()
-
-    e = ReraisedException(old_exc_value, prefix, suffix)
-
-    reraise_impl(e, traceback)
-
-# http://stackoverflow.com/a/13653312
-def full_class_name(o):
-    module = o.__class__.__module__
-    if module is None or module == str.__class__.__module__:
-        return o.__class__.__name__
-    return module + '.' + o.__class__.__name__
-
-class ReraisedException(Exception):
-    def __init__(self, old_exc, prefix, suffix):
-        self.old_exc = old_exc
-        self.prefix = prefix
-        self.suffix = suffix
-
-    def __str__(self):
-        klass = self.old_exc.__class__
-
-        orig = "%s: %s" % (full_class_name(self.old_exc), klass.__str__(self.old_exc))
-        prefixpart = suffixpart = ''
-        if self.prefix is not None:
-            prefixpart = self.prefix + "\n"
-        if self.suffix is not None:
-            suffixpart = "\n\n" + self.suffix
-        return "%sThe original exception was:\n\n%s%s" % (prefixpart, orig, suffixpart)

gym/utils/reraise_impl_py2.py

@@ -1,2 +0,0 @@
-def reraise_impl(e, traceback):
-    raise e.__class__, e, traceback

gym/utils/reraise_impl_py3.py

@@ -1,4 +0,0 @@
-# http://stackoverflow.com/a/33822606 -- `from None` disables Python 3'
-# semi-smart exception chaining, which we don't want in this case.
-def reraise_impl(e, traceback):
-    raise e.with_traceback(traceback) from None