diff --git a/tools/pyflakes.sh b/tools/pyflakes.sh
index 97121bb7..c0a40971 100755
--- a/tools/pyflakes.sh
+++ b/tools/pyflakes.sh
@@ -8,9 +8,10 @@ grep -Fn '.setlocale' ${PYFILES} && echo 'Error: do not use setlocale' && exit 5
 grep -Fn '__future__ import with_statement' ${PYFILES} && echo 'Error: with_statement useless as we do not support Python 2.5' &&  exit 6
 grep -nE '^[[:space:]]+except [[:alnum:] ]+,[[:alnum:] ]+' ${PYFILES} && echo 'Error: use new "as" way of naming exceptions' && exit 7
 grep -nE "^ *print " ${PYFILES} && echo 'Error: Use the print function' && exit 8
-grep -Fn ".has_key" ${PYFILES} && echo 'Error: Deprecated, use in' && exit 9
+grep -Fn ".has_key" ${PYFILES} && echo 'Error: Deprecated, use operator "in"' && exit 9
+grep -Fn "os.isatty" ${PYFILES} && echo 'Error: Use stream.isatty() instead of os.isatty(stream.fileno())' && exit 10
 MODULE_FILES=$(git ls-files|grep '^modules/.*\.py$'|tr '\n' ' ')
-grep -nE "^ *print(\(| )" ${MODULE_FILES} && echo 'Error: Use of print in modules is forbidden, use logger instead' && exit 10
+grep -nE "^ *print(\(| )" ${MODULE_FILES} && echo 'Error: Use of print in modules is forbidden, use logger instead' && exit 20
 
 FLAKE8=""
 if which flake8 >/dev/null 2>&1; then
diff --git a/weboob/applications/pastoob/pastoob.py b/weboob/applications/pastoob/pastoob.py
index 75dcc8be..6a65670e 100644
--- a/weboob/applications/pastoob/pastoob.py
+++ b/weboob/applications/pastoob/pastoob.py
@@ -105,7 +105,7 @@ class Pastoob(ReplApplication):
             output.write(paste.contents)
             # add a newline unless we are writing
             # in a file or in a pipe
-            if os.isatty(output.fileno()):
+            if output.isatty():
                 output.write('\n')
 
     def do_post(self, line):
diff --git a/weboob/applications/webcontentedit/webcontentedit.py b/weboob/applications/webcontentedit/webcontentedit.py
index d2a980f7..f10169fd 100644
--- a/weboob/applications/webcontentedit/webcontentedit.py
+++ b/weboob/applications/webcontentedit/webcontentedit.py
@@ -197,5 +197,5 @@ class WebContentEdit(ReplApplication):
 
         # add a newline unless we are writing
         # in a file or in a pipe
-        if os.isatty(output.fileno()):
+        if output.isatty():
             output.write('\n')
diff --git a/weboob/tools/application/console.py b/weboob/tools/application/console.py
index 080a1383..e8691d8f 100644
--- a/weboob/tools/application/console.py
+++ b/weboob/tools/application/console.py
@@ -64,7 +64,7 @@ class ConsoleApplication(Application):
 
     # shell escape strings
     if sys.platform == 'win32' \
-            or not os.isatty(sys.stdout.fileno()) \
+            or not sys.stdout.isatty() \
             or os.getenv('ANSI_COLORS_DISABLED') is not None:
         #workaround to disable bold
         BOLD   = ''
@@ -120,7 +120,7 @@ class ConsoleApplication(Application):
     def check_loaded_backends(self, default_config=None):
         while len(self.enabled_backends) == 0:
             print('Warning: there is currently no configured backend for %s' % self.APPNAME)
-            if not os.isatty(self.stdout.fileno()) or not self.ask('Do you want to configure backends?', default=True):
+            if not self.stdout.isatty() or not self.ask('Do you want to configure backends?', default=True):
                 return False
 
             self.prompt_create_backends(default_config)
diff --git a/weboob/tools/application/formatters/iformatter.py b/weboob/tools/application/formatters/iformatter.py
index 977e7632..9d033087 100644
--- a/weboob/tools/application/formatters/iformatter.py
+++ b/weboob/tools/application/formatters/iformatter.py
@@ -84,7 +84,7 @@ class IFormatter(object):
     NC = ConsoleApplication.NC
 
     def colored(self, string, color, attrs=None, on_color=None):
-        if self.outfile != sys.stdout or not (os.isatty(self.outfile.fileno())):
+        if self.outfile != sys.stdout or not self.outfile.isatty():
             return string
 
         if isinstance(attrs, basestring):
@@ -100,7 +100,7 @@ class IFormatter(object):
         self.outfile = outfile
         # XXX if stdin is not a tty, it seems that the command fails.
 
-        if os.isatty(sys.stdout.fileno()) and os.isatty(sys.stdin.fileno()):
+        if sys.stdout.isatty() and sys.stdin.isatty():
             if sys.platform == 'win32':
                 self.termrows = WConio.gettextinfo()[8]
             else: