Made installing a bit easier by moving imports into the code

Author: vbuterin

ethereum/__init__.py

@@ -1,6 +1,9 @@
 # -*- coding: utf-8 -*-
 # ############# version ##################
-from pkg_resources import get_distribution, DistributionNotFound
+try:
+    from pkg_resources import get_distribution, DistributionNotFound
+except:
+    DistributionNotFound = Exception
 import os.path
 import subprocess
 import re

ethereum/pow/ethpow.py

@@ -2,7 +2,6 @@
 from ethereum import utils
 import time
 import sys
-import sha3
 import warnings
 from collections import OrderedDict
 from ethereum.slogging import get_logger
@@ -41,6 +40,7 @@
 
 
 def get_cache(block_number):
+    import sha3
     while len(cache_seeds) <= block_number // EPOCH_LENGTH:
         cache_seeds.append(sha3.sha3_256(cache_seeds[-1]).digest())
     seed = cache_seeds[block_number // EPOCH_LENGTH]

ethereum/tools/testutils.py

@@ -3,7 +3,6 @@
 import os
 import json
 from ethereum.utils import encode_hex, str_to_bytes
-import pytest
 
 FILL = 1
 VERIFY = 2
@@ -36,6 +35,7 @@ def run_abi_test(params, mode):
         }
 
 def generate_test_params(testsource, metafunc, skip_func=None, exclude_func=None):
+    import pytest
     if ['filename', 'testname', 'testdata'] != metafunc.fixturenames:
         return