Get rid of superfluous AddressLookupError subclasses.

Both were named DepLookupError, but there's no need for such
a distinction, let alone two such distinctions...

Also removed some cruft from scrooge_gen.py, while in the
neighborhood.

Testing Done:
CI passes: https://travis-ci.org/pantsbuild/pants/builds/84618376

Reviewed at https://rbcommons.com/s/twitter/r/2959/

contrib/scrooge/src/python/pants/contrib/scrooge/tasks/scrooge_gen.py

@@ -17,16 +17,12 @@
 from pants.backend.jvm.targets.java_library import JavaLibrary
 from pants.backend.jvm.targets.scala_library import ScalaLibrary
 from pants.backend.jvm.tasks.nailgun_task import NailgunTask
-from pants.base.build_environment import get_buildroot
 from pants.base.exceptions import TargetDefinitionException, TaskError
-from pants.build_graph.address import Address
 from pants.build_graph.address_lookup_error import AddressLookupError
 from pants.option.custom_types import dict_option, list_option
 from pants.util.dirutil import safe_mkdir, safe_open
 from twitter.common.collections import OrderedSet
 
-from pants.contrib.scrooge.tasks.java_thrift_library_fingerprint_strategy import \
-  JavaThriftLibraryFingerprintStrategy
 from pants.contrib.scrooge.tasks.thrift_util import calculate_compile_sources
 
 
@@ -39,10 +35,6 @@ class ScroogeGen(SimpleCodegenTask, NailgunTask):
 
   DepInfo = namedtuple('DepInfo', ['service', 'structs'])
 
-  class DepLookupError(AddressLookupError):
-    """Thrown when a dependency can't be found."""
-    pass
-
   class PartialCmd(namedtuple('PC', ['language', 'rpc_style', 'namespace_map'])):
 
     @property
@@ -61,7 +53,8 @@ def relative_outdir(self):
   def register_options(cls, register):
     super(ScroogeGen, cls).register_options(register)
     register('--verbose', default=False, action='store_true', help='Emit verbose output.')
-    register('--strict', fingerprint=True, default=False, action='store_true', help='Enable strict compilation.')
+    register('--strict', fingerprint=True, default=False, action='store_true',
+             help='Enable strict compilation.')
     register('--jvm-options', default=[], advanced=True, type=list_option,
              help='Use these jvm options when running Scrooge.')
     register('--service-deps', default={}, advanced=True, type=dict_option,
@@ -111,8 +104,8 @@ def _resolve_deps(self, depmap):
         try:
           dependencies.update(self.context.resolve(depspec))
         except AddressLookupError as e:
-          raise self.DepLookupError("{message}\n  referenced from [{section}] key: "
-                                    "gen->deps->{category} in pants.ini".format(
+          raise AddressLookupError('{message}\n  referenced from [{section}] key: '
+                                   'gen->deps->{category} in pants.ini'.format(
                                       message=e,
                                       section=_CONFIG_SECTION,
                                       category=category
@@ -196,10 +189,9 @@ def gen(self, partial_cmd, invalid_targets):
                                   args=args,
                                   workunit_name='scrooge-gen')
         try:
+          # TODO: This entire block appears to have no effect.
           if 0 == returncode:
-            gen_files_for_source = self.parse_gen_file_map(gen_file_map_path, outdir)
-          else:
-            gen_files_for_source = None
+            self.parse_gen_file_map(gen_file_map_path, outdir)
         finally:
           os.remove(gen_file_map_path)
 

src/python/pants/backend/codegen/tasks/BUILD

@@ -130,7 +130,6 @@ python_library(
     '3rdparty/python/twitter/commons:twitter.common.collections',
     ':common',
     'src/python/pants/base:build_environment',
-    'src/python/pants/base:dep_lookup_error',
     'src/python/pants/base:workunit',
     'src/python/pants/build_graph',
     'src/python/pants/util:memo',

src/python/pants/backend/codegen/tasks/simple_codegen_task.py

@@ -13,7 +13,6 @@
 
 from pants.backend.core.tasks.task import Task
 from pants.base.build_environment import get_buildroot
-from pants.base.dep_lookup_error import DepLookupError
 from pants.base.exceptions import TaskError
 from pants.base.workunit import WorkUnitLabel
 from pants.build_graph.address import Address
@@ -296,7 +295,7 @@ def resolve_deps(self, unresolved_deps):
       try:
         deps.update(self.context.resolve(dep))
       except AddressLookupError as e:
-        raise DepLookupError('{message}\n  on dependency {dep}'.format(message=e, dep=dep))
+        raise AddressLookupError('{message}\n  on dependency {dep}'.format(message=e, dep=dep))
     return deps
 
   class CodegenStrategy(AbstractClass):

src/python/pants/backend/jvm/subsystems/BUILD

@@ -5,7 +5,6 @@ python_library(
   name = 'jvm_tool_mixin',
   sources = ['jvm_tool_mixin.py'],
   dependencies = [
-    'src/python/pants/base:dep_lookup_error',
     'src/python/pants/base:exceptions',
   ],
 )

src/python/pants/backend/jvm/subsystems/jvm_tool_mixin.py

@@ -8,7 +8,6 @@
 from collections import namedtuple
 from textwrap import dedent
 
-from pants.base.dep_lookup_error import DepLookupError
 from pants.base.exceptions import TaskError
 from pants.option.custom_types import target_option
 

src/python/pants/base/BUILD

@@ -77,14 +77,6 @@ python_library(
   ],
 )
 
-python_library(
-  name = 'dep_lookup_error',
-  dependencies = [
-    ':address_lookup_error',
-  ],
-  sources = ['dep_lookup_error.py'],
-)
-
 python_library(
   name = 'deprecated',
   sources = ['deprecated.py'],