diff --git a/.travis.yml b/.travis.yml
index de1ad63..7fe3108 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,11 +8,17 @@ before-install:
 
 install:
   - pip install -r requirements.txt
+  - git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
 
 script:
+  # Run the unittests
   - python -m unittest discover --start-directory stl/ --pattern "*_test.py"
   - python -m unittest discover --start-directory example/ --pattern "*_test.py"
 
+  # Run the linter
+  - depot_tools/pylint stl --ignore=parsetab.py,parser_test_proto_pb2.py
+  - depot_tools/pylint example --ignore=example_pb2.py
+
 notification:
   email:
     - sprockets-eng@googlegroups.com
diff --git a/stl/base.py b/stl/base.py
index 02b0b99..07ebe67 100644
--- a/stl/base.py
+++ b/stl/base.py
@@ -89,6 +89,9 @@ def __init__(self, name):
   def __eq__(self, other):
     return NamedObject.__eq__(self, other) and self.params == other.params
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class TypedObject(NamedObject):
   """Base class for all object with a type and name.
@@ -104,6 +107,9 @@ def __init__(self, name, type_):
   def __eq__(self, other):
     return NamedObject.__eq__(self, other) and self.type_ == other.type_
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class Const(TypedObject):
   """Constants.
@@ -333,6 +339,9 @@ def __init__(self, name, type_):
   def __str__(self):
     return 'PARAM %s(%s)' % (self.name, self.type_)
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class LocalVar(TypedObject):
   """Local variables.
@@ -352,6 +361,9 @@ def __init__(self, name, type_):
   def __str__(self):
     return 'LOCAL %s(%s)' % (self.name, self.type_)
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class Field(TypedObject):
   """Fields in messages or in roles.
@@ -384,6 +396,9 @@ def __str__(self):
       return 'FIELD-OPTIONAL %s(%s)' % (self.name, self.type_)
     return 'FIELD %s(%s)' % (self.name, self.type_)
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class Role(NamedObject):
   """Roles.
@@ -522,6 +537,9 @@ def Run(self):
       raise RuntimeError('Func does not contain a runnable function.')
     return self.func(*self.args)
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class FuncNoOp(Func):
   """External function doing nothing."""
@@ -532,6 +550,9 @@ def __init__(self, name):
   def Run(self):
     return True
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class FuncGetField(Func):
   """External function to get the value of a field either of Role or dictionary.
@@ -555,6 +576,9 @@ def __str__(self):
   def Run(self):
     return self.obj[self.field]
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class FuncSet(Func):
   """External function to set a value to a field of Role or to a LocalVar.
@@ -603,6 +627,9 @@ def SetValue(self, value):
     else:
       raise TypeError('Cannot SetValue on type %s' % type(self.obj))
 
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
+
 
 class FuncWithContext(Func):
   """External event function with context.
@@ -651,3 +678,6 @@ def Run(self):
     if self.context.test_source:
       return self.event.Wait(*new_args)
     return self.event.Fire(*new_args)
+
+  def Resolve(self, env, resolved_params):
+      raise NotImplementedError('Resolved() is not needed: ' + self.name)
diff --git a/stl/lexer.py b/stl/lexer.py
index 211f5ac..8d43e23 100644
--- a/stl/lexer.py
+++ b/stl/lexer.py
@@ -15,17 +15,10 @@
 
 """Lexing (tokenizing) a state transition (STL) spec."""
 
-# pylint: disable=g-doc-args
-# pylint: disable=g-docstring-missing-newline
-# pylint: disable=g-docstring-quotes
-# pylint: disable=g-no-space-after-docstring-summary
-# pylint: disable=g-short-docstring-punctuation
-# pylint: disable=g-short-docstring-space
-# pylint: disable=invalid-name
-# pylint: disable=unused-variable
 
 import logging
-import ply.lex  # pylint: disable=g-bad-import-order
+
+import ply.lex
 
 
 class StlSyntaxError(SyntaxError):
@@ -136,7 +129,7 @@ def t_error(self, t):
                   t.value[0])
     t.lexer.skip(1)
 
-  def debug(data):
-    """Print out all the tokens in |data|."""
+  def debug(self):
+    """Print out all the tokens from the lexer|."""
     for token in self.lexer.tokens():
       print token
diff --git a/stl/lib.py b/stl/lib.py
index f6670bf..ea8b7e0 100644
--- a/stl/lib.py
+++ b/stl/lib.py
@@ -293,11 +293,11 @@ class DifferentFrom(Qualifier):
   def __init__(self):
     Qualifier.__init__(self)
 
-  def Validate(self, value, prev):
+  def Validate(self, value, prev):  # pylint: disable=arguments-differ
     # This value must not match the previous one.
     return value != prev
 
-  def Generate(self, prev):
+  def Generate(self, prev):  # pylint: disable=arguments-differ
     rand = random.randint(0, 999999)
     if 'random-%s' % rand == prev:
       rand += 1
diff --git a/stl/message.py b/stl/message.py
index 7b431c7..d85886f 100644
--- a/stl/message.py
+++ b/stl/message.py
@@ -15,11 +15,12 @@
 
 import importlib
 import logging
+
 from google.protobuf import message
 from google.protobuf import reflection
 
-import stl.base  # pylint: disable=g-bad-import-order
-import stl.lib  # pylint: disable=g-bad-import-order
+import stl.base
+import stl.lib
 
 
 class Message(stl.base.NamedObject):
diff --git a/stl/parser.py b/stl/parser.py
index d5e4b12..fb14216 100644
--- a/stl/parser.py
+++ b/stl/parser.py
@@ -14,20 +14,12 @@
 # limitations under the License.
 """Parsing a state transition spec."""
 
-# pylint: disable=g-doc-args
-# pylint: disable=g-docstring-missing-newline
-# pylint: disable=g-docstring-quotes
-# pylint: disable=g-no-space-after-docstring-summary
-# pylint: disable=g-short-docstring-punctuation
-# pylint: disable=g-short-docstring-space
-# pylint: disable=invalid-name
-# pylint: disable=unused-variable
-
 import logging
-import ply.yacc  # pylint: disable=g-bad-import-order
 import pprint
 import sys
 
+import ply.yacc
+
 import stl.base
 import stl.event
 import stl.lexer
@@ -98,19 +90,22 @@ def p_const_def(self, p):
     """const_def : CONST type NAME ';'
                  | CONST type NAME '=' value ';' """
     if self._local_env['_curr_module'].HasDefinition(p[3]):
-      logging.error('[%s:%d] Duplicated const: %s', self._filename, p.lineno(3), p[3])
+      logging.error(
+              '[%s:%d] Duplicated const: %s', self._filename, p.lineno(3), p[3])
       return
     # TODO(byungchul): Type checking
     if len(p) == 5:
       self._local_env['_curr_module'].consts[p[3]] = stl.base.Const(p[3], p[2])
     else:
-      self._local_env['_curr_module'].consts[p[3]] = stl.base.Const(p[3], p[2], p[5])
+      self._local_env['_curr_module'].consts[p[3]] = (
+              stl.base.Const(p[3], p[2], p[5]))
 
   def p_role_def(self, p):
     """role_def : ROLE NAME '{' '}'
                 | ROLE NAME '{' role_fields '}' """
     if self._local_env['_curr_module'].HasDefinition(p[2]):
-      logging.error('[%s:%d] Duplicated role: %s', self._filename, p.lineno(2), p[2])
+      logging.error(
+              '[%s:%d] Duplicated role: %s', self._filename, p.lineno(2), p[2])
       return
     role = stl.base.Role(p[2])
     if len(p) >= 6:
@@ -142,7 +137,8 @@ def p_state_def(self, p):
     """state_def : STATE NAME params '{' names '}'
                  | STATE NAME params '{' names ',' '}' """
     if self._local_env['_curr_module'].HasDefinition(p[2]):
-      logging.error('[%s:%d] Duplicated state: %s', self._filename, p.lineno(2), p[2])
+      logging.error(
+              '[%s:%d] Duplicated state: %s', self._filename, p.lineno(2), p[2])
       return
     state_ = stl.state.State(p[2])
     state_.params = p[3]
@@ -249,7 +245,8 @@ def p_field_property_list(self, p):
     assert isinstance(p[1], dict)
     key, val = p[3]
     if key in p[1]:
-      logging.error('[%s:%d] Duplicated key: %s', self._filename, p.lineno(3), key)
+      logging.error(
+              '[%s:%d] Duplicated key: %s', self._filename, p.lineno(3), key)
       return
     p[1][key] = val
     p[0] = p[1]
diff --git a/stl/qualifier.py b/stl/qualifier.py
index e258353..19085c4 100644
--- a/stl/qualifier.py
+++ b/stl/qualifier.py
@@ -71,5 +71,6 @@ def __str__(self):
     return '%s b(%s)' % (Qualifier.__str__(self), self.external_name)
 
   def Resolve(self, env, resolved_params):
+    del env, resolved_params  # Unused.
     logging.log(1, 'Resolving ' + self.name)
     return self.external