Minor fixes (#29)

* Updated dependencies.

* Now secret and API key is None by default.

* If Codeforces returns 502 error the exception will be raised.

Author: VadVergasov

requirements.txt

@@ -1,5 +1,5 @@
 appdirs==1.4.4
-astroid==2.5.1
+astroid==2.5.2
 atomicwrites==1.4.0
 attrs==20.3.0
 black==20.8b1
@@ -8,12 +8,12 @@ certifi==2020.12.5
 chardet==4.0.0
 click==7.1.2
 colorama==0.4.4
-docutils==0.16
+docutils==0.17
 idna==2.10
-importlib-metadata==3.7.3
+importlib-metadata==3.10.0
 iniconfig==1.1.1
 isort==5.8.0
-keyring==23.0.0
+keyring==23.0.1
 lazy-object-proxy==1.6.0
 lxml==4.6.3
 mccabe==0.6.1
@@ -24,18 +24,18 @@ pkginfo==1.7.0
 pluggy==0.13.1
 py==1.10.0
 Pygments==2.8.1
-pylint==2.7.2
+pylint==2.7.4
 pyparsing==2.4.7
-pytest==6.2.2
+pytest==6.2.3
 pywin32-ctypes==0.2.0
 readme-renderer==29.0
-regex==2021.3.17
+regex==2021.4.4
 requests==2.25.1
 requests-toolbelt==0.9.1
 rfc3986==1.4.0
 six==1.15.0
 toml==0.10.2
-tqdm==4.59.0
+tqdm==4.60.0
 twine==3.4.1
 typed-ast==1.4.2
 typing-extensions==3.7.4.3