diff --git a/osm_common/sol004_package.py b/osm_common/sol004_package.py
index 7d402f5..e6b40b4 100644
--- a/osm_common/sol004_package.py
+++ b/osm_common/sol004_package.py
@@ -60,16 +60,16 @@
 import hashlib
 
 
-_METADATA_FILE_PATH = 'TOSCA-Metadata/TOSCA.meta'
-_METADATA_DESCRIPTOR_FIELD = 'Entry-Definitions'
-_METADATA_MANIFEST_FIELD = 'ETSI-Entry-Manifest'
-_METADATA_CHANGELOG_FIELD = 'ETSI-Entry-Change-Log'
-_METADATA_LICENSES_FIELD = 'ETSI-Entry-Licenses'
-_METADATA_DEFAULT_CHANGELOG_PATH = 'ChangeLog.txt'
-_METADATA_DEFAULT_LICENSES_PATH = 'Licenses'
-_MANIFEST_FILE_PATH_FIELD = 'Source'
-_MANIFEST_FILE_HASH_ALGORITHM_FIELD = 'Algorithm'
-_MANIFEST_FILE_HASH_DIGEST_FIELD = 'Hash'
+_METADATA_FILE_PATH = "TOSCA-Metadata/TOSCA.meta"
+_METADATA_DESCRIPTOR_FIELD = "Entry-Definitions"
+_METADATA_MANIFEST_FIELD = "ETSI-Entry-Manifest"
+_METADATA_CHANGELOG_FIELD = "ETSI-Entry-Change-Log"
+_METADATA_LICENSES_FIELD = "ETSI-Entry-Licenses"
+_METADATA_DEFAULT_CHANGELOG_PATH = "ChangeLog.txt"
+_METADATA_DEFAULT_LICENSES_PATH = "Licenses"
+_MANIFEST_FILE_PATH_FIELD = "Source"
+_MANIFEST_FILE_HASH_ALGORITHM_FIELD = "Algorithm"
+_MANIFEST_FILE_HASH_DIGEST_FIELD = "Hash"
 
 
 class SOL004PackageException(Exception):
@@ -77,7 +77,7 @@
 
 
 class SOL004Package:
-    def __init__(self, package_path=''):
+    def __init__(self, package_path=""):
         self._package_path = package_path
         self._package_metadata = self._parse_package_metadata()
         self._manifest_data = self._parse_manifest_data()
@@ -94,21 +94,29 @@
         except FileNotFoundError as e:
             raise e
         except (Exception, OSError) as e:
-            raise SOL004PackageException('Error parsing {}: {}'.format(_METADATA_FILE_PATH, e))
+            raise SOL004PackageException(
+                "Error parsing {}: {}".format(_METADATA_FILE_PATH, e)
+            )
 
     def _parse_package_metadata_without_metadata_dir(self):
         package_root_files = {f for f in os.listdir(self._package_path)}
-        package_root_yamls = [f for f in package_root_files if f.endswith('.yml') or f.endswith('.yaml')]
+        package_root_yamls = [
+            f for f in package_root_files if f.endswith(".yml") or f.endswith(".yaml")
+        ]
         if len(package_root_yamls) != 1:
-            error_msg = 'Error parsing package metadata: there should be exactly 1 descriptor YAML, found {}'
+            error_msg = "Error parsing package metadata: there should be exactly 1 descriptor YAML, found {}"
             raise SOL004PackageException(error_msg.format(len(package_root_yamls)))
         # TODO: Parse extra metadata from descriptor YAML?
-        return [{
-            _METADATA_DESCRIPTOR_FIELD: package_root_yamls[0],
-            _METADATA_MANIFEST_FIELD: '{}.mf'.format(os.path.splitext(package_root_yamls[0])[0]),
-            _METADATA_CHANGELOG_FIELD: _METADATA_DEFAULT_CHANGELOG_PATH,
-            _METADATA_LICENSES_FIELD: _METADATA_DEFAULT_LICENSES_PATH
-        }]
+        return [
+            {
+                _METADATA_DESCRIPTOR_FIELD: package_root_yamls[0],
+                _METADATA_MANIFEST_FIELD: "{}.mf".format(
+                    os.path.splitext(package_root_yamls[0])[0]
+                ),
+                _METADATA_CHANGELOG_FIELD: _METADATA_DEFAULT_CHANGELOG_PATH,
+                _METADATA_LICENSES_FIELD: _METADATA_DEFAULT_LICENSES_PATH,
+            }
+        ]
 
     def _parse_manifest_data(self):
         manifest_path = None
@@ -117,13 +125,17 @@
                 manifest_path = tosca_meta[_METADATA_MANIFEST_FIELD]
                 break
         else:
-            error_msg = 'Error parsing {}: no {} field on path'.format(_METADATA_FILE_PATH, _METADATA_MANIFEST_FIELD)
+            error_msg = "Error parsing {}: no {} field on path".format(
+                _METADATA_FILE_PATH, _METADATA_MANIFEST_FIELD
+            )
             raise SOL004PackageException(error_msg)
 
         try:
             return self._parse_file_in_blocks(manifest_path)
         except (Exception, OSError) as e:
-            raise SOL004PackageException('Error parsing {}: {}'.format(manifest_path, e))
+            raise SOL004PackageException(
+                "Error parsing {}: {}".format(manifest_path, e)
+            )
 
     def _get_package_file_full_path(self, file_relative_path):
         return os.path.join(self._package_path, file_relative_path)
@@ -131,16 +143,20 @@
     def _parse_file_in_blocks(self, file_relative_path):
         file_path = self._get_package_file_full_path(file_relative_path)
         with open(file_path) as f:
-            blocks = f.read().split('\n\n')
+            blocks = f.read().split("\n\n")
         parsed_blocks = map(yaml.safe_load, blocks)
         return [block for block in parsed_blocks if block is not None]
 
     def _get_package_file_manifest_data(self, file_relative_path):
         for file_data in self._manifest_data:
-            if file_data.get(_MANIFEST_FILE_PATH_FIELD, '') == file_relative_path:
+            if file_data.get(_MANIFEST_FILE_PATH_FIELD, "") == file_relative_path:
                 return file_data
 
-        error_msg = 'Error parsing {} manifest data: file not found on manifest file'.format(file_relative_path)
+        error_msg = (
+            "Error parsing {} manifest data: file not found on manifest file".format(
+                file_relative_path
+            )
+        )
         raise SOL004PackageException(error_msg)
 
     def get_package_file_hash_digest_from_manifest(self, file_relative_path):
@@ -149,7 +165,9 @@
         try:
             return file_manifest_data[_MANIFEST_FILE_HASH_DIGEST_FIELD]
         except Exception as e:
-            raise SOL004PackageException('Error parsing {} hash digest: {}'.format(file_relative_path, e))
+            raise SOL004PackageException(
+                "Error parsing {} hash digest: {}".format(file_relative_path, e)
+            )
 
     def get_package_file_hash_algorithm_from_manifest(self, file_relative_path):
         """Returns the hash algorithm of a file inside this package as specified on the manifest file."""
@@ -157,16 +175,19 @@
         try:
             return file_manifest_data[_MANIFEST_FILE_HASH_ALGORITHM_FIELD]
         except Exception as e:
-            raise SOL004PackageException('Error parsing {} hash digest: {}'.format(file_relative_path, e))
+            raise SOL004PackageException(
+                "Error parsing {} hash digest: {}".format(file_relative_path, e)
+            )
 
     @staticmethod
     def _get_hash_function_from_hash_algorithm(hash_algorithm):
-        function_to_algorithm = {
-            'SHA-256': hashlib.sha256,
-            'SHA-512': hashlib.sha512
-        }
+        function_to_algorithm = {"SHA-256": hashlib.sha256, "SHA-512": hashlib.sha512}
         if hash_algorithm not in function_to_algorithm:
-            error_msg = 'Error checking hash function: hash algorithm {} not supported'.format(hash_algorithm)
+            error_msg = (
+                "Error checking hash function: hash algorithm {} not supported".format(
+                    hash_algorithm
+                )
+            )
             raise SOL004PackageException(error_msg)
         return function_to_algorithm[hash_algorithm]
 
@@ -177,16 +198,24 @@
             with open(file_path, "rb") as f:
                 return hash_function(f.read()).hexdigest()
         except Exception as e:
-            raise SOL004PackageException('Error hashing {}: {}'.format(file_relative_path, e))
+            raise SOL004PackageException(
+                "Error hashing {}: {}".format(file_relative_path, e)
+            )
 
     def validate_package_file_hash(self, file_relative_path):
         """Validates the integrity of a file using the hash algorithm and digest on the package manifest."""
-        hash_algorithm = self.get_package_file_hash_algorithm_from_manifest(file_relative_path)
+        hash_algorithm = self.get_package_file_hash_algorithm_from_manifest(
+            file_relative_path
+        )
         file_hash = self._calculate_file_hash(file_relative_path, hash_algorithm)
-        expected_file_hash = self.get_package_file_hash_digest_from_manifest(file_relative_path)
+        expected_file_hash = self.get_package_file_hash_digest_from_manifest(
+            file_relative_path
+        )
         if file_hash != expected_file_hash:
-            error_msg = 'Error validating {} hash: calculated hash {} is different than manifest hash {}'
-            raise SOL004PackageException(error_msg.format(file_relative_path, file_hash, expected_file_hash))
+            error_msg = "Error validating {} hash: calculated hash {} is different than manifest hash {}"
+            raise SOL004PackageException(
+                error_msg.format(file_relative_path, file_hash, expected_file_hash)
+            )
 
     def validate_package_hashes(self):
         """Validates the integrity of all files listed on the package manifest."""
@@ -201,5 +230,7 @@
             if _METADATA_DESCRIPTOR_FIELD in tosca_meta:
                 return tosca_meta[_METADATA_DESCRIPTOR_FIELD]
 
-        error_msg = 'Error: no {} entry found on {}'.format(_METADATA_DESCRIPTOR_FIELD, _METADATA_FILE_PATH)
+        error_msg = "Error: no {} entry found on {}".format(
+            _METADATA_DESCRIPTOR_FIELD, _METADATA_FILE_PATH
+        )
         raise SOL004PackageException(error_msg)