Add better messages on environment variable error

Otherwise it doesn't indicate the name of the environment variable in
the result output:

    Error: Error(EnvVar(NotPresent), State { next_error: None, backtrace: InternalBacktrace { backtrace: None } })

2 files changed, 4 insertions, 2 deletions

diff --git a/license-generator/src/database.rs b/license-generator/src/database.rs
index 94e925f..505a788 100644
--- a/license-generator/src/database.rs
+++ b/license-generator/src/database.rs
@@ -5,7 +5,8 @@ use mysql;
 use errors::*;
 
 pub fn get_database_connection() -> Result<mysql::PooledConn> {
-    let connection_url = env::var("DATABASE_URL")?;
+    let connection_url = env::var("DATABASE_URL")
+        .chain_err(|| "DATABASE_URL environment variable not found")?;
     let pool = mysql::Pool::new_manual(10, 50, connection_url)?;
     let cx = pool.get_conn()?;
 
diff --git a/license-generator/src/main.rs b/license-generator/src/main.rs
index 5c1a0aa..d428af4 100644
--- a/license-generator/src/main.rs
+++ b/license-generator/src/main.rs
@@ -18,7 +18,8 @@ use license_generator::errors::*;
 use license_generator::purchaser::Purchaser;
 
 fn main() -> Result<()> {
-    let log_file_path = env::var("LOG_FILE")?;
+    let log_file_path = env::var("LOG_FILE")
+        .chain_err(|| "LOG_FILE environment variable not found")?;
 
     let log_file = OpenOptions::new()
         .append(true)