pixiv: fix failbooru when uploading bad pixiv id posts.

Fixes an "incompatible character encodings: UTF-8 and ASCII-8BIT"
exception when uploading a deleted Pixiv post.

Caused by the Pixiv API error message not having the encoding set to UTF-8.

app/logical/pixiv_api_client.rb

@@ -141,12 +141,13 @@ class PixivApiClient
 
     url = "https://public-api.secure.pixiv.net/v#{API_VERSION}/works/#{illust_id.to_i}.json"
     resp = HTTParty.get(url, Danbooru.config.httparty_options.deep_merge(query: params, headers: headers))
+    body = resp.body.force_encoding("utf-8")
 
     if resp.success?
-      json = parse_api_json(resp.body)
+      json = parse_api_json(body)
       WorksResponse.new(json["response"][0])
     else
-      raise Error.new("Pixiv API call failed (status=#{resp.code} body=#{resp.body})")
+      raise Error.new("Pixiv API call failed (status=#{resp.code} body=#{body})")
     end
   end
 
@@ -177,11 +178,13 @@ private
       url = "https://oauth.secure.pixiv.net/auth/token"
 
       resp = HTTParty.post(url, Danbooru.config.httparty_options.deep_merge(body: params, headers: headers))
+      body = resp.body.force_encoding("utf-8")
+
       if resp.success?
-        json = JSON.parse(resp.body)
+        json = JSON.parse(body)
         access_token = json["response"]["access_token"]
       else
-        raise Error.new("Pixiv API access token call failed (status=#{resp.code} body=#{resp.body})")
+        raise Error.new("Pixiv API access token call failed (status=#{resp.code} body=#{body})")
       end
 
       access_token

app/views/static/error.html.erb

@@ -1,7 +1,7 @@
 <% if CurrentUser.user.is_builder? && @exception.present? %>
   <h1><%= @exception.class.to_s %> exception raised</h1>
   <ul style="font-family: monospace; font-size: 1.2em; list-style-type: none;">
-    <li><%= @exception.message %></li>
+    <li><%= @exception.message.force_encoding("utf-8") %></li>
     <%- Rails.backtrace_cleaner.clean(@exception.backtrace).each do |b| -%>
       <li style="list-style-type: none;"><%= b %></li>
     <%- end -%>
@@ -9,5 +9,5 @@
 <% elsif @error_message %>
   <p><%= @error_message %></p>
 <% else %>
-  <p><%= @exception.message %></p>
+  <p><%= @exception.message.force_encoding("utf-8") %></p>
 <% end %>