title: Axios fails with unclear erros while browser can request API
body: <p>I want to make simple get request to my API deployed to Heroku. Here is how: </p>
  
  <pre><code>axios.get(my_url_here).then(res =&gt; this.topics = res.data).catch(e =&gt; {
           print(JSON.stringify(e)); 
       }); 
  </code></pre>
  
  <p>But, only catch works and it prints following:</p>
  
  <pre><code>{"message":"Network Error","name":"Error","stack":"Error: Network Error\n at createError (webpack-internal:///./node_modules/axios/lib/core/createError.js:16:15)\n at XMLHttpRequest.handleError (webpack-internal:///./node_modules/axios/lib/adapters/xhr.js:83:14)","config":{"url":"my_url_here","method":"get","headers":{"Accept":"application/json, text/plain, */*"},"transformRequest":[null],"transformResponse":[null],"timeout":0,"xsrfCookieName":"XSRF-TOKEN","xsrfHeaderName":"X-XSRF-TOKEN","maxContentLength":-1}}
  </code></pre>
  
  <p>That error does not say anything. I couldn't find good materials about it, but some of them tells that it is a problem related to cors. I don't have any code related to <code>Allow-origin</code> stuff on my API, but how the web browser successfully makes requests? And why axios fails and cannot make that requests? I tried to use <code>cors</code> library on my server-side but when I deployed code to Heroku, it just stopped working. What can be the reason for above error and how to solve it? </p>