update r3945 with more descriptive error message

src/http/modules/ngx_http_fastcgi_module.c

diff --git a/src/http/modules/ngx_http_fastcgi_module.c b/src/http/modules/ngx_http_fastcgi_module.c
index 12d5b1d..71194fd 100644
--- a/src/http/modules/ngx_http_fastcgi_module.c
+++ b/src/http/modules/ngx_http_fastcgi_module.c
@@ -2003,6 +2003,8 @@
 
     conf->catch_stderr = NGX_CONF_UNSET_PTR;
 
+    ngx_str_set(&conf->upstream.module, "fastcgi");
+
     return conf;
 }
 

src/http/modules/ngx_http_proxy_module.c

diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index 214fe6a..147422a 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -1707,6 +1707,8 @@
     conf->headers_hash_max_size = NGX_CONF_UNSET_UINT;
     conf->headers_hash_bucket_size = NGX_CONF_UNSET_UINT;
 
+    ngx_str_set(&conf->upstream.module, "proxy");
+
     return conf;
 }
 

src/http/modules/ngx_http_scgi_module.c

diff --git a/src/http/modules/ngx_http_scgi_module.c b/src/http/modules/ngx_http_scgi_module.c
index d745551..c83d770 100644
--- a/src/http/modules/ngx_http_scgi_module.c
+++ b/src/http/modules/ngx_http_scgi_module.c
@@ -1030,6 +1030,8 @@
     /* "scgi_cyclic_temp_file" is disabled */
     conf->upstream.cyclic_temp_file = 0;
 
+    ngx_str_set(&conf->upstream.module, "scgi");
+
     return conf;
 }
 

src/http/modules/ngx_http_uwsgi_module.c

diff --git a/src/http/modules/ngx_http_uwsgi_module.c b/src/http/modules/ngx_http_uwsgi_module.c
index cd3c7c1..a907e53 100644
--- a/src/http/modules/ngx_http_uwsgi_module.c
+++ b/src/http/modules/ngx_http_uwsgi_module.c
@@ -1083,6 +1083,8 @@
     /* "uwsgi_cyclic_temp_file" is disabled */
     conf->upstream.cyclic_temp_file = 0;
 
+    ngx_str_set(&conf->upstream.module, "uwsgi");
+
     return conf;
 }