Reformat error messages.

One line per error message.

src/main.cpp

@@ -32,12 +32,14 @@
 #include <cstdint>
 #include <cstdlib>
 #include <exception>
+#include <fstream>
 #include <future>
 #include <iostream>
 #include <locale>
 #include <mutex>
 #include <string>
 #include <string_view>
+#include <system_error>
 #include <thread>
 #include <vector>
 
@@ -70,8 +72,8 @@ int main(int argc, char *argv[])
     }
     catch (std::exception &e)
     { // Exceptions we can't recover from or ones we don't know.
-        cerr << translate("ERROR: ") << e.what() << '\n';
-        cerr << translate("Error while parsing options.") << '\n';
+        cerr << translate("ERROR: ") << e.what();
+        cerr << translate(" (while parsing options)") << '\n';
         return EXIT_FAILURE;
     }
 
@@ -150,17 +152,33 @@ int main(int argc, char *argv[])
                 catch (const zip::exception &e)
                 {
                     if (opts.ignore_archive_errors && e.code == 1)
-                    {
+                    { // File is probably not an EPUB.
                         return EXIT_SUCCESS;
                     }
 
-                    cerr << translate("ERROR: ") << e.what() << '\n';
-                    cerr << format(translate("Error while searching {0:s}.")
-                                       .str(),
+                    cerr << translate("ERROR: ") << e.what();
+                    cerr << format(translate(" (while searching {0:s})").str(),
                                    filepath)
                          << '\n';
                     return EXIT_FAILURE;
                 }
+                catch (const std::ifstream::failure &e)
+                {
+                    cerr << translate("ERROR: ");
+                    if (e.code() == std::errc::permission_denied)
+                    {
+                        cerr << translate("Permission denied.");
+                    }
+                    else
+                    { // std::ifstream seems to always return a generic error?
+                        cerr << translate("Probably permission denied.") << " ("
+                             << e.what() << ')';
+                    }
+
+                    cerr << format(translate(" (while opening {0:s})").str(),
+                                   filepath)
+                         << '\n';
+                }
             }
 
             return EXIT_SUCCESS;

src/zip.cpp

@@ -106,16 +106,10 @@ std::string read_file(const fs::path &filepath, std::string_view entry_path)
 
 struct archive *open_file(const fs::path &filepath)
 {
-    std::ifstream file{filepath};
-    if (!file.good())
-    {
-        exception e{format(translate("Could not open {0:s}: "
-                                     "Permission denied.")
-                               .str(),
-                           filepath.string())};
-        e.code = 2;
-        throw exception{e};
-    }
+    // Throw exception if we can't open the file.
+    std::ifstream file;
+    file.exceptions(std::ios::failbit);
+    file.open(filepath);
     file.close();
 
     auto *zipfile{archive_read_new()};