Improve output of validation

Made the output more redable by listing the errors, being less verbose
and using colors to signal success/failure.

Dockerfile

@@ -1,5 +1,5 @@
 FROM circleci/python:3.6-jessie
 
-RUN sudo pip install openapi-spec-validator
+RUN sudo pip install openapi-spec-validator ansicolors
 
 COPY validator.py /opt/

validator.py

@@ -1,10 +1,70 @@
 import sys
+from jsonschema.exceptions import RefResolutionError
+from colors import color
 from os import path, getcwd
-from openapi_spec_validator import validate_spec_url
+from openapi_spec_validator.handlers import UrlHandler
+from openapi_spec_validator import openapi_v3_spec_validator
 
 
 def validate(file_name):
-    validate_spec_url('file://' + path.join(getcwd(), file_name))
+    counter = 0
+
+    try:
+        handler = UrlHandler('file')
+        url = 'file://' + path.join(getcwd(), file_name)
+        spec = handler(url)
+
+        for i in openapi_v3_spec_validator.iter_errors(spec, spec_url=url):
+            counter += 1
+            print_error(
+                counter,
+                ':'.join(i.absolute_path),
+                i.message,
+                i.instance
+            )
+
+    except RefResolutionError as e:
+        counter += 1
+        print_error(
+            counter,
+            '',
+            f'Unable to resolve {e.__context__.args[0]} in {e.args[0]}',
+            ''
+        )
+    except:
+        counter += 1
+        print_error(counter, '', sys.exc_info()[0], '')
+    finally:
+        if counter > 0:
+            print()
+            print(
+                color(
+                    ' [FAIL] %d errors found ' % counter,
+                    fg='white',
+                    bg='red',
+                    style='bold'
+                )
+            )
+            return 1
+        else:
+            print(
+                color(
+                    ' [PASS] No errors found ',
+                    fg='white',
+                    bg='green',
+                    style='bold'
+                )
+            )
+            return 0
+
+
+def print_error(count, path, message, instance):
+    print()
+    print(
+        color('Error #%d in [%s]:' % (count, path or 'unknown'), style='bold')
+    )
+    print("    %s" % message)
+    print("    %s" % instance)
 
 
 def help():
@@ -17,7 +77,7 @@ def main(argv):
         help()
         sys.exit(2)
 
-    validate(argv[0])
+    sys.exit(validate(argv[0]))
 
 
 if __name__ == "__main__":