diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -16,6 +16,7 @@ from .i18n import _
 from .node import nullid, short
 
 from . import (
+    encoding,
     error,
     formatter,
     match,
@@ -165,7 +166,7 @@ def _picktool(repo, ui, path, binary, sy
                 return (force, force)
 
     # HGMERGE takes next precedence
-    hgmerge = os.environ.get("HGMERGE")
+    hgmerge = encoding.environ.get("HGMERGE")
     if hgmerge:
         if changedelete and not supportscd(hgmerge):
             return ":prompt", None
diff --git a/mercurial/hgweb/common.py b/mercurial/hgweb/common.py
--- a/mercurial/hgweb/common.py
+++ b/mercurial/hgweb/common.py
@@ -13,6 +13,7 @@ import mimetypes
 import os
 
 from .. import (
+    encoding,
     pycompat,
     util,
 )
@@ -191,7 +192,7 @@ def get_contact(config):
     """
     return (config("web", "contact") or
             config("ui", "username") or
-            os.environ.get("EMAIL") or "")
+            encoding.environ.get("EMAIL") or "")
 
 def caching(web, req):
     tag = 'W/"%s"' % web.mtime
diff --git a/mercurial/hgweb/hgweb_mod.py b/mercurial/hgweb/hgweb_mod.py
--- a/mercurial/hgweb/hgweb_mod.py
+++ b/mercurial/hgweb/hgweb_mod.py
@@ -286,7 +286,8 @@ class hgweb(object):
         Modern servers should be using WSGI and should avoid this
         method, if possible.
         """
-        if not os.environ.get('GATEWAY_INTERFACE', '').startswith("CGI/1."):
+        if not encoding.environ.get('GATEWAY_INTERFACE',
+                                    '').startswith("CGI/1."):
             raise RuntimeError("This function is only intended to be "
                                "called while running as a CGI script.")
         wsgicgi.launch(self)
diff --git a/mercurial/hgweb/hgwebdir_mod.py b/mercurial/hgweb/hgwebdir_mod.py
--- a/mercurial/hgweb/hgwebdir_mod.py
+++ b/mercurial/hgweb/hgwebdir_mod.py
@@ -186,7 +186,8 @@ class hgwebdir(object):
         self.lastrefresh = time.time()
 
     def run(self):
-        if not os.environ.get('GATEWAY_INTERFACE', '').startswith("CGI/1."):
+        if not encoding.environ.get('GATEWAY_INTERFACE',
+                                    '').startswith("CGI/1."):
             raise RuntimeError("This function is only intended to be "
                                "called while running as a CGI script.")
         wsgicgi.launch(self)
diff --git a/mercurial/hgweb/wsgicgi.py b/mercurial/hgweb/wsgicgi.py
--- a/mercurial/hgweb/wsgicgi.py
+++ b/mercurial/hgweb/wsgicgi.py
@@ -10,9 +10,8 @@
 
 from __future__ import absolute_import
 
-import os
-
 from .. import (
+    encoding,
     util,
 )
 
@@ -24,7 +23,7 @@ def launch(application):
     util.setbinary(util.stdin)
     util.setbinary(util.stdout)
 
-    environ = dict(os.environ.iteritems())
+    environ = dict(encoding.environ.iteritems())
     environ.setdefault('PATH_INFO', '')
     if environ.get('SERVER_SOFTWARE', '').startswith('Microsoft-IIS'):
         # IIS includes script_name in PATH_INFO
diff --git a/mercurial/url.py b/mercurial/url.py
--- a/mercurial/url.py
+++ b/mercurial/url.py
@@ -15,6 +15,7 @@ import socket
 
 from .i18n import _
 from . import (
+    encoding,
     error,
     httpconnection as httpconnectionmod,
     keepalive,
@@ -118,8 +119,8 @@ class proxyhandler(urlreq.proxyhandler):
         if ui.config("http_proxy", "host"):
             for env in ["HTTP_PROXY", "http_proxy", "no_proxy"]:
                 try:
-                    if env in os.environ:
-                        del os.environ[env]
+                    if env in encoding.environ:
+                        del encoding.environ[env]
                 except OSError:
                     pass
 
diff --git a/mercurial/windows.py b/mercurial/windows.py
--- a/mercurial/windows.py
+++ b/mercurial/windows.py
@@ -177,7 +177,7 @@ def _is_win_9x():
     try:
         return sys.getwindowsversion()[3] == 1
     except AttributeError:
-        return 'command' in os.environ.get('comspec', '')
+        return 'command' in encoding.environ.get('comspec', '')
 
 def openhardlinks():
     return not _is_win_9x()
@@ -303,7 +303,7 @@ def findexe(command):
     PATH isn't searched if command is an absolute or relative path.
     An extension from PATHEXT is found and added if not present.
     If command isn't found None is returned.'''
-    pathext = os.environ.get('PATHEXT', '.COM;.EXE;.BAT;.CMD')
+    pathext = encoding.environ.get('PATHEXT', '.COM;.EXE;.BAT;.CMD')
     pathexts = [ext for ext in pathext.lower().split(pycompat.ospathsep)]
     if os.path.splitext(command)[1].lower() in pathexts:
         pathexts = ['']
@@ -319,7 +319,7 @@ def findexe(command):
     if pycompat.ossep in command:
         return findexisting(command)
 
-    for path in os.environ.get('PATH', '').split(pycompat.ospathsep):
+    for path in encoding.environ.get('PATH', '').split(pycompat.ospathsep):
         executable = findexisting(os.path.join(path, command))
         if executable is not None:
             return executable