Allow overriding environment variables for credstore invocation

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.6
+FROM python:3.6.4
 RUN apt-get update && apt-get -y install \
     gnupg2 \
     pass \

dockerpycreds/store.py

@@ -6,17 +6,19 @@
 
 from . import constants
 from . import errors
+from .utils import create_environment_dict
 from .utils import find_executable
 
 
 class Store(object):
-    def __init__(self, program):
+    def __init__(self, program, environment=None):
         """ Create a store object that acts as an interface to
             perform the basic operations for storing, retrieving
             and erasing credentials using `program`.
         """
         self.program = constants.PROGRAM_PREFIX + program
         self.exe = find_executable(self.program)
+        self.environment = environment
         if self.exe is None:
             raise errors.InitializationError(
                 '{0} not installed or not available in PATH'.format(
@@ -65,15 +67,16 @@ def erase(self, server):
 
     def _execute(self, subcmd, data_input):
         output = None
+        env = create_environment_dict(self.environment)
         try:
             if six.PY3:
                 output = subprocess.check_output(
-                    [self.exe, subcmd], input=data_input
+                    [self.exe, subcmd], input=data_input, env=env,
                 )
             else:
                 process = subprocess.Popen(
                     [self.exe, subcmd], stdin=subprocess.PIPE,
-                    stdout=subprocess.PIPE
+                    stdout=subprocess.PIPE, env=env,
                 )
                 output, err = process.communicate(data_input)
                 if process.returncode != 0:

dockerpycreds/utils.py

@@ -5,7 +5,7 @@
 
 def find_executable(executable, path=None):
     """
-    As distutils.spawn.find_executable, but on Windows, looks up
+    As distutils.spawn.find_executable, but on Windows, look up
     every extension declared in PATHEXT instead of just `.exe`
     """
     if sys.platform != 'win32':
@@ -27,3 +27,12 @@ def find_executable(executable, path=None):
         return None
     else:
         return executable
+
+
+def create_environment_dict(overrides):
+    """
+    Create and return a copy of os.environ with the specified overrides
+    """
+    result = os.environ.copy()
+    result.update(overrides or {})
+    return result

tests/store_test.py

@@ -1,3 +1,4 @@
+import os
 import random
 import sys
 
@@ -67,3 +68,10 @@ def test_unicode_strings(self):
         self.store.erase(key)
         with pytest.raises(CredentialsNotFound):
             self.store.get(key)
+
+    def test_execute_with_env_override(self):
+        self.store.exe = 'env'
+        self.store.environment = {'FOO': 'bar'}
+        data = self.store._execute('--null', '')
+        assert b'\0FOO=bar\0' in data
+        assert 'FOO' not in os.environ

tests/utils_test.py

@@ -0,0 +1,22 @@
+import os
+
+from dockerpycreds.utils import create_environment_dict
+
+try:
+    from unittest import mock
+except ImportError:
+    import mock
+
+
+@mock.patch.dict(os.environ)
+def test_create_environment_dict():
+    base = {'FOO': 'bar', 'BAZ': 'foobar'}
+    os.environ = base
+    assert create_environment_dict({'FOO': 'baz'}) == {
+        'FOO': 'baz', 'BAZ': 'foobar',
+    }
+    assert create_environment_dict({'HELLO': 'world'}) == {
+        'FOO': 'bar', 'BAZ': 'foobar', 'HELLO': 'world',
+    }
+
+    assert os.environ == base