Rephrase WinHttp-based exceptions to be more humane

Increase required C++REST SDK version to 2.10.8, because it fixes a bug that affects code
in this commit:
microsoft/cpprestsdk@aabec3c

configure.ac

@@ -79,7 +79,7 @@ AS_IF([test "x$with_cpprest" != "xno"],
       CPPFLAGS="$CPPFLAGS $CXXFLAGS $BOOST_CPPFLAGS"
           AC_CHECK_HEADERS([cpprest/http_client.h],
               [
-                  AC_MSG_CHECKING([for libcpprest >= 2.5])
+                  AC_MSG_CHECKING([for libcpprest >= 2.10.8])
                   old_LIBS="$LIBS"
                   LIBS="-lcpprest $BOOST_SYSTEM_LIB $BOOST_THREAD_LIB -lssl -lcrypto $LIBS"
                   AC_LINK_IFELSE([AC_LANG_PROGRAM(
@@ -88,8 +88,8 @@ AS_IF([test "x$with_cpprest" != "xno"],
                           #include <cpprest/http_client.h>
                       ],
                       [
-                          #if CPPREST_VERSION < 200500
-                            #error "cpprest >= 2.5 required"
+                          #if CPPREST_VERSION < 201008
+                            #error "cpprest >= 2.10.8 required"
                           #endif
                           web::http::client::http_client c(U("https://poedit.net"));
                       ])],

src/Poedit-Prefix.pch

@@ -12,7 +12,7 @@
 
     #include "concurrency.h"
     #include "configuration.h"
-
+    #include "errors.h"
     #include "unicode_helpers.h"
     #include "str_helpers.h"
 #endif

src/errors.cpp

@@ -25,6 +25,34 @@
 
 #include "errors.h"
 
+#include <wx/translation.h>
+
+#ifndef __WXOSX__
+#include <cpprest/http_client.h>
+#include <boost/algorithm/string.hpp>
+#endif
+
+namespace
+{
+
+inline wxString from_c_string(const char *msg)
+{
+    // try interpreting as UTF-8 first as the most likely one (from external sources)
+    wxString s = wxString::FromUTF8(msg);
+    if (!s.empty())
+        return s;
+
+    s = wxString(msg);
+    if (!s.empty())
+        return s;
+
+    // not in current locale either, fall back to Latin1
+    return wxString(msg, wxConvISO8859_1);
+}
+
+} // anonymous namespace
+
+
 wxString errors::detail::DescribeExceptionImpl(Rethrower& rethrower)
 {
     try
@@ -36,21 +64,32 @@ wxString errors::detail::DescribeExceptionImpl(Rethrower& rethrower)
     {
         return e.What();
     }
-    catch (const std::exception& e)
+#ifndef __WXOSX__
+    catch (const web::http::http_exception & e)
     {
-        const char *msg = e.what();
-        // try interpreting as UTF-8 first as the most likely one (from external sources)
-        wxString s = wxString::FromUTF8(msg);
-        if (s.empty())
+        // rephrase the errors more humanly; the default form is too cryptic
+        // also strip trailing newlines that C++REST tends to add
+        std::string msg(e.what());
+        if (!boost::starts_with(msg, "WinHttp"))
         {
-            s = wxString(msg);
-            if (s.empty()) // not in current locale either, fall back to Latin1
-                s = wxString(msg, wxConvISO8859_1);
+            boost::trim_right(msg);
+            return from_c_string(msg.c_str());  // preserve actual messages
         }
-        return s;
+
+        msg = e.error_code().message();
+        if (msg.empty())
+            return from_c_string(e.what());  // give up
+
+        boost::trim_right(msg);
+        return wxString::Format(_("Network error: %s (%d)"), from_c_string(msg.c_str()), e.error_code().value());
+    }
+#endif // !__WXOSX__
+    catch (const std::exception& e)
+    {
+        return from_c_string(e.what());
     }
     catch (...)
     {
-        return "unknown error";
+        return _("Unknown error");
     }
 }